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	$62.26	3.513%	$64.4472	$64.45	$64.45	$64.40
Purchase #2	$55.72	11.203%	$61.9623	$61.96	$61.95	$62.00
Purchase #3	$50.38	10.156%	$55.4966	$55.50	$55.50	$55.50
Purchase #4	$101.50	10.154%	$111.8063	$111.81	$111.80	$111.80
Purchase #5	$149.60	8.729%	$162.6586	$162.66	$162.65	$162.70
Purchase #6	$94.80	9.317%	$103.6325	$103.63	$103.65	$103.60
Purchase #7	$18.31	8.179%	$19.8076	$19.81	$19.80	$19.80
7 purchase totals =	$532.57		$579.8111	$579.82	$579.80	$579.80