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	$104.90	12.240%	$117.7398	$117.74	$117.75	$117.70
Purchase #2	$72.98	10.409%	$80.5765	$80.58	$80.60	$80.60
Purchase #3	$23.33	4.525%	$24.3857	$24.39	$24.40	$24.40
Purchase #4	$116.74	8.388%	$126.5322	$126.53	$126.55	$126.50
Purchase #5	$110.93	11.240%	$123.3985	$123.40	$123.40	$123.40
Purchase #6	$6.60	13.144%	$7.4675	$7.47	$7.45	$7.50
Purchase #7	$138.41	6.488%	$147.39	$147.39	$147.40	$147.40
7 purchase totals =	$573.89		$627.4902	$627.50	$627.55	$627.50