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	$162.77	13.266%	$184.3631	$184.36	$184.35	$184.40
Purchase #2	$58.48	10.474%	$64.6052	$64.61	$64.60	$64.60
Purchase #3	$101.73	9.400%	$111.2926	$111.29	$111.30	$111.30
Purchase #4	$99.31	5.857%	$105.1266	$105.13	$105.15	$105.10
Purchase #5	$151.62	9.163%	$165.5129	$165.51	$165.50	$165.50
Purchase #6	$243.95	8.472%	$264.6174	$264.62	$264.60	$264.60
Purchase #7	$135.47	4.362%	$141.3792	$141.38	$141.40	$141.40
7 purchase totals =	$953.33		$1,036.8970	$1,036.90	$1,036.90	$1,036.90