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	$86.41	3.873%	$89.7567	$89.76	$89.75	$89.80
Purchase #2	$165.84	4.717%	$173.6627	$173.66	$173.65	$173.70
Purchase #3	$215.40	4.844%	$225.834	$225.83	$225.85	$225.80
Purchase #4	$62.95	11.842%	$70.4045	$70.40	$70.40	$70.40
Purchase #5	$236.48	11.808%	$264.4036	$264.40	$264.40	$264.40
Purchase #6	$49.49	10.281%	$54.5781	$54.58	$54.60	$54.60
Purchase #7	$115.60	7.698%	$124.4989	$124.50	$124.50	$124.50
7 purchase totals =	$932.17		$1,003.1385	$1,003.13	$1,003.15	$1,003.20