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	$139.63	6.549%	$148.7744	$148.77	$148.75	$148.80
Purchase #2	$249.53	12.641%	$281.0731	$281.07	$281.05	$281.10
Purchase #3	$233.56	4.517%	$244.1099	$244.11	$244.10	$244.10
Purchase #4	$17.32	3.340%	$17.8985	$17.90	$17.90	$17.90
Purchase #5	$31.42	5.179%	$33.0472	$33.05	$33.05	$33.00
Purchase #6	$40.54	6.388%	$43.1297	$43.13	$43.15	$43.10
Purchase #7	$119.31	7.682%	$128.4754	$128.48	$128.50	$128.50
7 purchase totals =	$831.31		$896.5082	$896.51	$896.50	$896.50