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	$165.96	3.308%	$171.45	$171.45	$171.45	$171.50
Purchase #2	$90.52	4.591%	$94.6758	$94.68	$94.70	$94.70
Purchase #3	$188.42	13.502%	$213.8605	$213.86	$213.85	$213.90
Purchase #4	$105.95	3.660%	$109.8278	$109.83	$109.85	$109.80
Purchase #5	$24.67	11.603%	$27.5325	$27.53	$27.55	$27.50
Purchase #6	$82.53	12.722%	$93.0295	$93.03	$93.05	$93.00
Purchase #7	$80.33	10.686%	$88.9141	$88.91	$88.90	$88.90
7 purchase totals =	$738.38		$799.2902	$799.29	$799.35	$799.30