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	$225.53	4.271%	$235.1624	$235.16	$235.15	$235.20
Purchase #2	$63.61	9.110%	$69.4049	$69.40	$69.40	$69.40
Purchase #3	$81.26	12.476%	$91.398	$91.40	$91.40	$91.40
Purchase #4	$50.71	5.530%	$53.5143	$53.51	$53.50	$53.50
Purchase #5	$243.73	13.205%	$275.9145	$275.91	$275.90	$275.90
Purchase #6	$205.30	5.345%	$216.2733	$216.27	$216.25	$216.30
Purchase #7	$209.76	6.613%	$223.6314	$223.63	$223.65	$223.60
7 purchase totals =	$1,079.90		$1,165.2988	$1,165.28	$1,165.25	$1,165.30