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	$205.47	6.481%	$218.7865	$218.79	$218.80	$218.80
Purchase #2	$175.57	8.825%	$191.0641	$191.06	$191.05	$191.10
Purchase #3	$223.81	11.772%	$250.1569	$250.16	$250.15	$250.20
Purchase #4	$224.55	13.322%	$254.4646	$254.46	$254.45	$254.50
Purchase #5	$60.38	9.724%	$66.2514	$66.25	$66.25	$66.30
Purchase #6	$208.35	6.868%	$222.6595	$222.66	$222.65	$222.70
Purchase #7	$239.96	4.298%	$250.2735	$250.27	$250.25	$250.30
7 purchase totals =	$1,338.09		$1,453.6565	$1,453.65	$1,453.60	$1,453.90