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	$64.49	11.416%	$71.8522	$71.85	$71.85	$71.90
Purchase #2	$207.60	7.495%	$223.1596	$223.16	$223.15	$223.20
Purchase #3	$209.89	8.332%	$227.378	$227.38	$227.40	$227.40
Purchase #4	$61.51	11.710%	$68.7128	$68.71	$68.70	$68.70
Purchase #5	$104.56	6.248%	$111.0929	$111.09	$111.10	$111.10
Purchase #6	$110.68	11.391%	$123.2876	$123.29	$123.30	$123.30
Purchase #7	$163.31	5.705%	$172.6268	$172.63	$172.65	$172.60
7 purchase totals =	$922.04		$998.1099	$998.11	$998.15	$998.20