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	$133.25	13.709%	$151.5172	$151.52	$151.50	$151.50
Purchase #2	$101.35	10.778%	$112.2735	$112.27	$112.25	$112.30
Purchase #3	$230.53	13.818%	$262.3846	$262.38	$262.40	$262.40
Purchase #4	$108.42	7.676%	$116.7423	$116.74	$116.75	$116.70
Purchase #5	$175.70	11.263%	$195.4891	$195.49	$195.50	$195.50
Purchase #6	$169.54	9.609%	$185.8311	$185.83	$185.85	$185.80
Purchase #7	$122.45	12.115%	$137.2848	$137.28	$137.30	$137.30
7 purchase totals =	$1,041.24		$1,161.5226	$1,161.51	$1,161.55	$1,161.50