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	$78.82	11.592%	$87.9568	$87.96	$87.95	$88.00
Purchase #2	$170.41	13.626%	$193.6301	$193.63	$193.65	$193.60
Purchase #3	$10.48	8.526%	$11.3735	$11.37	$11.35	$11.40
Purchase #4	$135.51	11.342%	$150.8795	$150.88	$150.90	$150.90
Purchase #5	$119.88	6.848%	$128.0894	$128.09	$128.10	$128.10
Purchase #6	$74.41	4.206%	$77.5397	$77.54	$77.55	$77.50
Purchase #7	$77.89	13.766%	$88.6123	$88.61	$88.60	$88.60
7 purchase totals =	$667.40		$738.0813	$738.08	$738.10	$738.10