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	$217.28	3.802%	$225.541	$225.54	$225.55	$225.50
Purchase #2	$223.71	5.381%	$235.7478	$235.75	$235.75	$235.70
Purchase #3	$138.28	6.217%	$146.8769	$146.88	$146.90	$146.90
Purchase #4	$219.84	6.182%	$233.4305	$233.43	$233.45	$233.40
Purchase #5	$214.67	12.350%	$241.1817	$241.18	$241.20	$241.20
Purchase #6	$79.83	11.556%	$89.0552	$89.06	$89.05	$89.10
Purchase #7	$99.61	12.872%	$112.4318	$112.43	$112.45	$112.40
7 purchase totals =	$1,193.22		$1,284.2649	$1,284.27	$1,284.35	$1,284.20