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	$127.53	3.207%	$131.6199	$131.62	$131.60	$131.60
Purchase #2	$124.83	8.870%	$135.9024	$135.90	$135.90	$135.90
Purchase #3	$35.37	6.679%	$37.7324	$37.73	$37.75	$37.70
Purchase #4	$124.63	11.676%	$139.1818	$139.18	$139.20	$139.20
Purchase #5	$149.91	10.674%	$165.9114	$165.91	$165.90	$165.90
Purchase #6	$85.33	7.724%	$91.9209	$91.92	$91.90	$91.90
Purchase #7	$14.85	13.743%	$16.8908	$16.89	$16.90	$16.90
7 purchase totals =	$662.45		$719.1596	$719.15	$719.15	$719.10