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	$200.29	11.557%	$223.4375	$223.44	$223.45	$223.40
Purchase #2	$151.60	5.317%	$159.6606	$159.66	$159.65	$159.70
Purchase #3	$216.52	3.366%	$223.8081	$223.81	$223.80	$223.80
Purchase #4	$238.40	11.211%	$265.127	$265.13	$265.15	$265.10
Purchase #5	$140.47	6.463%	$149.5486	$149.55	$149.55	$149.50
Purchase #6	$68.70	12.445%	$77.2497	$77.25	$77.25	$77.20
Purchase #7	$39.29	3.354%	$40.6078	$40.61	$40.60	$40.60
7 purchase totals =	$1,055.27		$1,139.4393	$1,139.45	$1,139.45	$1,139.30