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	$165.30	12.142%	$185.3707	$185.37	$185.35	$185.40
Purchase #2	$180.77	5.821%	$191.2926	$191.29	$191.30	$191.30
Purchase #3	$83.39	5.722%	$88.1616	$88.16	$88.15	$88.20
Purchase #4	$143.57	11.318%	$159.8193	$159.82	$159.80	$159.80
Purchase #5	$166.64	13.352%	$188.8898	$188.89	$188.90	$188.90
Purchase #6	$65.55	6.584%	$69.8658	$69.87	$69.85	$69.90
Purchase #7	$18.66	7.852%	$20.1252	$20.13	$20.15	$20.10
7 purchase totals =	$823.88		$903.5250	$903.53	$903.50	$903.60