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	$120.52	9.596%	$132.0851	$132.09	$132.10	$132.10
Purchase #2	$48.38	11.190%	$53.7937	$53.79	$53.80	$53.80
Purchase #3	$144.69	13.824%	$164.6919	$164.69	$164.70	$164.70
Purchase #4	$196.89	11.138%	$218.8196	$218.82	$218.80	$218.80
Purchase #5	$57.84	13.240%	$65.498	$65.50	$65.50	$65.50
Purchase #6	$244.49	4.651%	$255.8612	$255.86	$255.85	$255.90
Purchase #7	$61.86	5.870%	$65.4912	$65.49	$65.50	$65.50
7 purchase totals =	$874.67		$956.2407	$956.24	$956.25	$956.30