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	$144.34	8.737%	$156.951	$156.95	$156.95	$157.00
Purchase #2	$89.49	12.710%	$100.8642	$100.86	$100.85	$100.90
Purchase #3	$71.86	6.820%	$76.7609	$76.76	$76.75	$76.80
Purchase #4	$87.55	13.548%	$99.4113	$99.41	$99.40	$99.40
Purchase #5	$143.32	10.594%	$158.5033	$158.50	$158.50	$158.50
Purchase #6	$50.91	3.740%	$52.814	$52.81	$52.80	$52.80
Purchase #7	$32.37	8.678%	$35.1791	$35.18	$35.20	$35.20
7 purchase totals =	$619.84		$680.4838	$680.47	$680.45	$680.60