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	$203.34	4.583%	$212.6591	$212.66	$212.65	$212.70
Purchase #2	$64.79	12.537%	$72.9127	$72.91	$72.90	$72.90
Purchase #3	$62.46	13.287%	$70.7591	$70.76	$70.75	$70.80
Purchase #4	$62.33	12.545%	$70.1493	$70.15	$70.15	$70.10
Purchase #5	$37.51	11.386%	$41.7809	$41.78	$41.80	$41.80
Purchase #6	$149.56	5.863%	$158.3287	$158.33	$158.35	$158.30
Purchase #7	$45.26	6.655%	$48.2721	$48.27	$48.25	$48.30
7 purchase totals =	$625.25		$674.8619	$674.86	$674.85	$674.90