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	$56.76	5.471%	$59.8653	$59.87	$59.85	$59.90
Purchase #2	$250.85	13.527%	$284.7825	$284.78	$284.80	$284.80
Purchase #3	$124.69	5.551%	$131.6115	$131.61	$131.60	$131.60
Purchase #4	$214.76	5.123%	$225.7622	$225.76	$225.75	$225.80
Purchase #5	$39.28	8.303%	$42.5414	$42.54	$42.55	$42.50
Purchase #6	$32.68	3.137%	$33.7052	$33.71	$33.70	$33.70
Purchase #7	$217.96	13.473%	$247.3258	$247.33	$247.35	$247.30
7 purchase totals =	$936.98		$1,025.5939	$1,025.60	$1,025.60	$1,025.60