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	$195.87	12.257%	$219.8778	$219.88	$219.90	$219.90
Purchase #2	$65.96	9.619%	$72.3047	$72.30	$72.30	$72.30
Purchase #3	$105.58	13.257%	$119.5767	$119.58	$119.60	$119.60
Purchase #4	$146.91	8.137%	$158.8641	$158.86	$158.85	$158.90
Purchase #5	$242.27	4.583%	$253.3732	$253.37	$253.35	$253.40
Purchase #6	$156.39	7.601%	$168.2772	$168.28	$168.30	$168.30
Purchase #7	$22.85	10.733%	$25.3025	$25.30	$25.30	$25.30
7 purchase totals =	$935.83		$1,017.5762	$1,017.57	$1,017.60	$1,017.70