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	$151.78	10.624%	$167.9051	$167.91	$167.90	$167.90
Purchase #2	$29.42	9.227%	$32.1346	$32.13	$32.15	$32.10
Purchase #3	$159.26	13.115%	$180.1469	$180.15	$180.15	$180.10
Purchase #4	$184.91	3.404%	$191.2043	$191.20	$191.20	$191.20
Purchase #5	$54.29	9.373%	$59.3786	$59.38	$59.40	$59.40
Purchase #6	$53.88	12.503%	$60.6166	$60.62	$60.60	$60.60
Purchase #7	$233.44	8.689%	$253.7236	$253.72	$253.70	$253.70
7 purchase totals =	$866.98		$945.1097	$945.11	$945.10	$945.00