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	$234.44	10.107%	$258.1349	$258.13	$258.15	$258.10
Purchase #2	$125.51	11.405%	$139.8244	$139.82	$139.80	$139.80
Purchase #3	$99.62	5.572%	$105.1708	$105.17	$105.15	$105.20
Purchase #4	$39.38	4.124%	$41.004	$41.00	$41.00	$41.00
Purchase #5	$131.36	13.287%	$148.8138	$148.81	$148.80	$148.80
Purchase #6	$250.54	9.851%	$275.2207	$275.22	$275.20	$275.20
Purchase #7	$182.68	9.188%	$199.4646	$199.46	$199.45	$199.50
7 purchase totals =	$1,063.53		$1,167.6332	$1,167.61	$1,167.55	$1,167.60