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	$33.96	9.391%	$37.1492	$37.15	$37.15	$37.10
Purchase #2	$189.57	5.587%	$200.1613	$200.16	$200.15	$200.20
Purchase #3	$10.39	7.147%	$11.1326	$11.13	$11.15	$11.10
Purchase #4	$228.91	10.353%	$252.6091	$252.61	$252.60	$252.60
Purchase #5	$222.56	5.406%	$234.5916	$234.59	$234.60	$234.60
Purchase #6	$132.84	5.329%	$139.919	$139.92	$139.90	$139.90
Purchase #7	$112.47	12.573%	$126.6109	$126.61	$126.60	$126.60
7 purchase totals =	$930.70		$1,002.1737	$1,002.17	$1,002.15	$1,002.10