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	$225.50	9.764%	$247.5178	$247.52	$247.50	$247.50
Purchase #2	$124.90	13.573%	$141.8527	$141.85	$141.85	$141.90
Purchase #3	$63.81	12.474%	$71.7697	$71.77	$71.75	$71.80
Purchase #4	$80.41	11.215%	$89.428	$89.43	$89.45	$89.40
Purchase #5	$50.61	10.308%	$55.8269	$55.83	$55.85	$55.80
Purchase #6	$59.74	10.596%	$66.0701	$66.07	$66.05	$66.10
Purchase #7	$193.56	5.523%	$204.2503	$204.25	$204.25	$204.30
7 purchase totals =	$798.53		$876.7155	$876.72	$876.70	$876.80