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	$59.54	10.428%	$65.7488	$65.75	$65.75	$65.70
Purchase #2	$90.31	7.565%	$97.142	$97.14	$97.15	$97.10
Purchase #3	$31.86	13.563%	$36.1812	$36.18	$36.20	$36.20
Purchase #4	$33.41	6.725%	$35.6568	$35.66	$35.65	$35.70
Purchase #5	$163.93	13.411%	$185.9147	$185.91	$185.90	$185.90
Purchase #6	$87.78	13.255%	$99.4152	$99.42	$99.40	$99.40
Purchase #7	$54.87	8.815%	$59.7068	$59.71	$59.70	$59.70
7 purchase totals =	$521.70		$579.7655	$579.77	$579.75	$579.70