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	$74.49	11.305%	$82.9111	$82.91	$82.90	$82.90
Purchase #2	$184.74	12.772%	$208.335	$208.34	$208.35	$208.30
Purchase #3	$182.62	13.122%	$206.5834	$206.58	$206.60	$206.60
Purchase #4	$220.90	9.468%	$241.8148	$241.81	$241.80	$241.80
Purchase #5	$166.59	13.317%	$188.7748	$188.77	$188.75	$188.80
Purchase #6	$196.50	13.456%	$222.941	$222.94	$222.95	$222.90
Purchase #7	$216.72	13.563%	$246.1137	$246.11	$246.10	$246.10
7 purchase totals =	$1,242.56		$1,397.4738	$1,397.46	$1,397.45	$1,397.40