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	$138.92	5.717%	$146.8621	$146.86	$146.85	$146.90
Purchase #2	$150.91	9.146%	$164.7122	$164.71	$164.70	$164.70
Purchase #3	$171.25	8.130%	$185.1726	$185.17	$185.15	$185.20
Purchase #4	$140.49	4.321%	$146.5606	$146.56	$146.55	$146.60
Purchase #5	$58.40	3.553%	$60.475	$60.48	$60.50	$60.50
Purchase #6	$167.57	3.372%	$173.2205	$173.22	$173.20	$173.20
Purchase #7	$137.58	4.632%	$143.9527	$143.95	$143.95	$144.00
7 purchase totals =	$965.12		$1,020.9557	$1,020.95	$1,020.90	$1,021.10