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	$175.70	8.443%	$190.5344	$190.53	$190.55	$190.50
Purchase #2	$19.48	6.818%	$20.8081	$20.81	$20.80	$20.80
Purchase #3	$196.58	6.762%	$209.8727	$209.87	$209.85	$209.90
Purchase #4	$192.71	5.417%	$203.1491	$203.15	$203.15	$203.10
Purchase #5	$17.62	4.717%	$18.4511	$18.45	$18.45	$18.50
Purchase #6	$39.69	6.580%	$42.3016	$42.30	$42.30	$42.30
Purchase #7	$180.56	5.672%	$190.8014	$190.80	$190.80	$190.80
7 purchase totals =	$822.34		$875.9184	$875.91	$875.90	$875.90