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	$216.31	3.158%	$223.1411	$223.14	$223.15	$223.10
Purchase #2	$217.27	13.801%	$247.2554	$247.26	$247.25	$247.30
Purchase #3	$62.29	9.547%	$68.2368	$68.24	$68.25	$68.20
Purchase #4	$32.44	4.385%	$33.8625	$33.86	$33.85	$33.90
Purchase #5	$223.69	4.404%	$233.5413	$233.54	$233.55	$233.50
Purchase #6	$198.56	5.404%	$209.2902	$209.29	$209.30	$209.30
Purchase #7	$37.83	5.335%	$39.8482	$39.85	$39.85	$39.80
7 purchase totals =	$988.39		$1,055.1755	$1,055.18	$1,055.20	$1,055.10