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	$104.36	8.434%	$113.1617	$113.16	$113.15	$113.20
Purchase #2	$59.50	5.406%	$62.7166	$62.72	$62.70	$62.70
Purchase #3	$138.50	3.747%	$143.6896	$143.69	$143.70	$143.70
Purchase #4	$146.84	4.470%	$153.4037	$153.40	$153.40	$153.40
Purchase #5	$149.86	3.776%	$155.5187	$155.52	$155.50	$155.50
Purchase #6	$140.27	7.221%	$150.3989	$150.40	$150.40	$150.40
Purchase #7	$136.34	5.276%	$143.5333	$143.53	$143.55	$143.50
7 purchase totals =	$875.67		$922.4225	$922.42	$922.40	$922.40