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	$163.89	10.750%	$181.5082	$181.51	$181.50	$181.50
Purchase #2	$55.38	5.758%	$58.5688	$58.57	$58.55	$58.60
Purchase #3	$181.27	8.363%	$196.4296	$196.43	$196.45	$196.40
Purchase #4	$58.96	12.646%	$66.4161	$66.42	$66.40	$66.40
Purchase #5	$125.29	12.653%	$141.1429	$141.14	$141.15	$141.10
Purchase #6	$84.77	8.375%	$91.8695	$91.87	$91.85	$91.90
Purchase #7	$137.64	9.280%	$150.413	$150.41	$150.40	$150.40
7 purchase totals =	$807.20		$886.3481	$886.35	$886.30	$886.30