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	$146.41	9.609%	$160.4785	$160.48	$160.50	$160.50
Purchase #2	$142.77	6.333%	$151.8116	$151.81	$151.80	$151.80
Purchase #3	$100.93	7.114%	$108.1102	$108.11	$108.10	$108.10
Purchase #4	$54.30	8.839%	$59.0996	$59.10	$59.10	$59.10
Purchase #5	$69.61	8.765%	$75.7113	$75.71	$75.70	$75.70
Purchase #6	$40.85	9.604%	$44.7732	$44.77	$44.75	$44.80
Purchase #7	$130.58	13.380%	$148.0516	$148.05	$148.05	$148.10
7 purchase totals =	$685.45		$748.0360	$748.03	$748.00	$748.10