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	$197.82	13.176%	$223.8848	$223.88	$223.90	$223.90
Purchase #2	$20.54	4.433%	$21.4505	$21.45	$21.45	$21.50
Purchase #3	$100.61	8.144%	$108.8037	$108.80	$108.80	$108.80
Purchase #4	$152.46	4.376%	$159.1316	$159.13	$159.15	$159.10
Purchase #5	$55.94	6.538%	$59.5974	$59.60	$59.60	$59.60
Purchase #6	$76.91	7.349%	$82.5621	$82.56	$82.55	$82.60
Purchase #7	$134.37	6.856%	$143.5824	$143.58	$143.60	$143.60
7 purchase totals =	$738.65		$799.0125	$799.00	$799.05	$799.10