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	$135.39	10.746%	$149.939	$149.94	$149.95	$149.90
Purchase #2	$140.56	11.108%	$156.1734	$156.17	$156.15	$156.20
Purchase #3	$228.31	11.721%	$255.0702	$255.07	$255.05	$255.10
Purchase #4	$52.68	13.150%	$59.6074	$59.61	$59.60	$59.60
Purchase #5	$12.53	12.111%	$14.0475	$14.05	$14.05	$14.00
Purchase #6	$214.69	8.793%	$233.5677	$233.57	$233.55	$233.60
Purchase #7	$60.83	4.776%	$63.7352	$63.74	$63.75	$63.70
7 purchase totals =	$844.99		$932.1404	$932.15	$932.10	$932.10