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	$65.83	11.598%	$73.465	$73.47	$73.45	$73.50
Purchase #2	$113.71	11.730%	$127.0482	$127.05	$127.05	$127.00
Purchase #3	$61.45	8.691%	$66.7906	$66.79	$66.80	$66.80
Purchase #4	$58.29	6.183%	$61.8941	$61.89	$61.90	$61.90
Purchase #5	$53.73	10.445%	$59.3421	$59.34	$59.35	$59.30
Purchase #6	$216.49	7.408%	$232.5276	$232.53	$232.55	$232.50
Purchase #7	$92.47	7.138%	$99.0705	$99.07	$99.05	$99.10
7 purchase totals =	$661.97		$720.1381	$720.14	$720.15	$720.10