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	$196.61	12.187%	$220.5709	$220.57	$220.55	$220.60
Purchase #2	$109.52	11.673%	$122.3043	$122.30	$122.30	$122.30
Purchase #3	$170.31	11.504%	$189.9025	$189.90	$189.90	$189.90
Purchase #4	$116.55	10.325%	$128.5838	$128.58	$128.60	$128.60
Purchase #5	$218.36	5.846%	$231.1253	$231.13	$231.15	$231.10
Purchase #6	$64.39	10.735%	$71.3023	$71.30	$71.30	$71.30
Purchase #7	$91.56	8.797%	$99.6145	$99.61	$99.60	$99.60
7 purchase totals =	$967.30		$1,063.4036	$1,063.39	$1,063.40	$1,063.40