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	$31.92	3.851%	$33.1492	$33.15	$33.15	$33.10
Purchase #2	$50.43	11.171%	$56.0635	$56.06	$56.05	$56.10
Purchase #3	$101.82	11.496%	$113.5252	$113.53	$113.55	$113.50
Purchase #4	$75.69	12.524%	$85.1694	$85.17	$85.15	$85.20
Purchase #5	$78.71	6.146%	$83.5475	$83.55	$83.55	$83.50
Purchase #6	$21.61	5.624%	$22.8253	$22.83	$22.85	$22.80
Purchase #7	$58.93	10.695%	$65.2326	$65.23	$65.25	$65.20
7 purchase totals =	$419.11		$459.5127	$459.52	$459.55	$459.40