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	$172.85	13.520%	$196.2193	$196.22	$196.20	$196.20
Purchase #2	$50.84	12.539%	$57.2148	$57.21	$57.20	$57.20
Purchase #3	$186.63	4.606%	$195.2262	$195.23	$195.25	$195.20
Purchase #4	$228.84	8.191%	$247.5843	$247.58	$247.60	$247.60
Purchase #5	$52.60	11.580%	$58.6911	$58.69	$58.70	$58.70
Purchase #6	$77.88	5.828%	$82.4188	$82.42	$82.40	$82.40
Purchase #7	$37.91	5.594%	$40.0307	$40.03	$40.05	$40.00
7 purchase totals =	$807.55		$877.3852	$877.38	$877.40	$877.30