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	$99.78	11.803%	$111.557	$111.56	$111.55	$111.60
Purchase #2	$73.33	11.670%	$81.8876	$81.89	$81.90	$81.90
Purchase #3	$225.28	8.584%	$244.618	$244.62	$244.60	$244.60
Purchase #4	$194.57	7.275%	$208.725	$208.73	$208.75	$208.70
Purchase #5	$74.34	11.506%	$82.8936	$82.89	$82.90	$82.90
Purchase #6	$189.50	7.369%	$203.4643	$203.46	$203.45	$203.50
Purchase #7	$146.60	3.654%	$151.9568	$151.96	$151.95	$152.00
7 purchase totals =	$1,003.40		$1,085.1023	$1,085.11	$1,085.10	$1,085.20