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	$196.87	10.809%	$218.1497	$218.15	$218.15	$218.10
Purchase #2	$50.47	7.563%	$54.287	$54.29	$54.30	$54.30
Purchase #3	$172.57	9.417%	$188.8209	$188.82	$188.80	$188.80
Purchase #4	$105.81	10.707%	$117.1391	$117.14	$117.15	$117.10
Purchase #5	$29.87	8.222%	$32.3259	$32.33	$32.35	$32.30
Purchase #6	$151.72	6.417%	$161.4559	$161.46	$161.45	$161.50
Purchase #7	$110.47	12.229%	$123.9794	$123.98	$124.00	$124.00
7 purchase totals =	$817.78		$896.1579	$896.17	$896.20	$896.10