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	$188.88	4.388%	$197.1681	$197.17	$197.15	$197.20
Purchase #2	$133.55	8.472%	$144.8644	$144.86	$144.85	$144.90
Purchase #3	$40.98	4.795%	$42.945	$42.95	$42.95	$42.90
Purchase #4	$94.84	5.204%	$99.7755	$99.78	$99.80	$99.80
Purchase #5	$148.34	13.201%	$167.9224	$167.92	$167.90	$167.90
Purchase #6	$199.31	3.532%	$206.3496	$206.35	$206.35	$206.30
Purchase #7	$49.92	8.569%	$54.1976	$54.20	$54.20	$54.20
7 purchase totals =	$855.82		$913.2226	$913.23	$913.20	$913.20