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	$153.91	11.200%	$171.1479	$171.15	$171.15	$171.10
Purchase #2	$232.32	5.873%	$245.9642	$245.96	$245.95	$246.00
Purchase #3	$59.70	9.668%	$65.4718	$65.47	$65.45	$65.50
Purchase #4	$146.65	10.628%	$162.236	$162.24	$162.25	$162.20
Purchase #5	$208.47	4.634%	$218.1305	$218.13	$218.15	$218.10
Purchase #6	$104.35	6.759%	$111.403	$111.40	$111.40	$111.40
Purchase #7	$171.91	10.680%	$190.27	$190.27	$190.25	$190.30
7 purchase totals =	$1,077.31		$1,164.6234	$1,164.62	$1,164.60	$1,164.60