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	$123.32	6.105%	$130.8487	$130.85	$130.85	$130.80
Purchase #2	$72.25	13.675%	$82.1302	$82.13	$82.15	$82.10
Purchase #3	$231.54	8.753%	$251.8067	$251.81	$251.80	$251.80
Purchase #4	$10.91	3.213%	$11.2605	$11.26	$11.25	$11.30
Purchase #5	$170.59	12.288%	$191.5521	$191.55	$191.55	$191.60
Purchase #6	$246.65	13.222%	$279.2621	$279.26	$279.25	$279.30
Purchase #7	$79.51	8.746%	$86.4639	$86.46	$86.45	$86.50
7 purchase totals =	$934.77		$1,033.3242	$1,033.32	$1,033.30	$1,033.40