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	$106.37	4.610%	$111.2737	$111.27	$111.25	$111.30
Purchase #2	$214.71	11.492%	$239.3845	$239.38	$239.40	$239.40
Purchase #3	$64.50	10.595%	$71.3338	$71.33	$71.35	$71.30
Purchase #4	$203.89	5.449%	$215	$215.00	$215.00	$215.00
Purchase #5	$153.46	10.269%	$169.2188	$169.22	$169.20	$169.20
Purchase #6	$57.40	5.508%	$60.5616	$60.56	$60.55	$60.60
Purchase #7	$247.58	11.144%	$275.1703	$275.17	$275.15	$275.20
7 purchase totals =	$1,047.91		$1,141.9427	$1,141.93	$1,141.90	$1,142.00