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	$66.88	4.540%	$69.9164	$69.92	$69.90	$69.90
Purchase #2	$85.48	11.550%	$95.3529	$95.35	$95.35	$95.40
Purchase #3	$79.33	7.466%	$85.2528	$85.25	$85.25	$85.30
Purchase #4	$225.74	8.279%	$244.429	$244.43	$244.45	$244.40
Purchase #5	$64.67	11.485%	$72.0973	$72.10	$72.10	$72.10
Purchase #6	$146.37	3.274%	$151.1622	$151.16	$151.15	$151.20
Purchase #7	$143.39	9.738%	$157.3533	$157.35	$157.35	$157.40
7 purchase totals =	$811.86		$875.5639	$875.56	$875.55	$875.70