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	$59.55	5.123%	$62.6007	$62.60	$62.60	$62.60
Purchase #2	$157.76	11.701%	$176.2195	$176.22	$176.20	$176.20
Purchase #3	$5.41	10.171%	$5.9603	$5.96	$5.95	$6.00
Purchase #4	$146.41	10.765%	$162.171	$162.17	$162.15	$162.20
Purchase #5	$240.70	7.350%	$258.3915	$258.39	$258.40	$258.40
Purchase #6	$152.87	3.757%	$158.6133	$158.61	$158.60	$158.60
Purchase #7	$241.71	10.668%	$267.4956	$267.50	$267.50	$267.50
7 purchase totals =	$1,004.41		$1,091.4519	$1,091.45	$1,091.40	$1,091.50