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	$201.86	10.237%	$222.5244	$222.52	$222.50	$222.50
Purchase #2	$34.93	8.329%	$37.8393	$37.84	$37.85	$37.80
Purchase #3	$124.45	6.536%	$132.5841	$132.58	$132.60	$132.60
Purchase #4	$147.68	3.843%	$153.3553	$153.36	$153.35	$153.40
Purchase #5	$99.67	11.739%	$111.3703	$111.37	$111.35	$111.40
Purchase #6	$101.78	11.684%	$113.672	$113.67	$113.65	$113.70
Purchase #7	$135.51	11.541%	$151.1492	$151.15	$151.15	$151.10
7 purchase totals =	$845.88		$922.4946	$922.49	$922.45	$922.50