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	$129.47	10.782%	$143.4295	$143.43	$143.45	$143.40
Purchase #2	$200.97	10.808%	$222.6908	$222.69	$222.70	$222.70
Purchase #3	$120.48	13.843%	$137.158	$137.16	$137.15	$137.20
Purchase #4	$139.37	8.701%	$151.4966	$151.50	$151.50	$151.50
Purchase #5	$69.34	3.851%	$72.0103	$72.01	$72.00	$72.00
Purchase #6	$67.98	11.126%	$75.5435	$75.54	$75.55	$75.50
Purchase #7	$139.72	4.760%	$146.3707	$146.37	$146.35	$146.40
7 purchase totals =	$867.33		$948.6994	$948.70	$948.70	$948.70