Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$139.62	12.851%	$157.5626	$157.56	$157.55	$157.60
Purchase #2	$88.78	12.513%	$99.889	$99.89	$99.90	$99.90
Purchase #3	$178.82	6.740%	$190.8725	$190.87	$190.85	$190.90
Purchase #4	$123.71	11.246%	$137.6224	$137.62	$137.60	$137.60
Purchase #5	$250.31	13.290%	$283.5762	$283.58	$283.60	$283.60
Purchase #6	$193.70	11.551%	$216.0743	$216.07	$216.05	$216.10
Purchase #7	$34.36	4.172%	$35.7935	$35.79	$35.80	$35.80
7 purchase totals =	$1,009.30		$1,121.3905	$1,121.38	$1,121.35	$1,121.50