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	$70.25	9.803%	$77.1366	$77.14	$77.15	$77.10
Purchase #2	$150.67	9.652%	$165.2127	$165.21	$165.20	$165.20
Purchase #3	$69.41	13.469%	$78.7588	$78.76	$78.75	$78.80
Purchase #4	$85.56	10.401%	$94.4591	$94.46	$94.45	$94.50
Purchase #5	$105.50	13.235%	$119.4629	$119.46	$119.45	$119.50
Purchase #6	$13.90	11.557%	$15.5064	$15.51	$15.50	$15.50
Purchase #7	$126.46	11.797%	$141.3785	$141.38	$141.40	$141.40
7 purchase totals =	$621.75		$691.9150	$691.92	$691.90	$692.00