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	$246.70	7.162%	$264.3687	$264.37	$264.35	$264.40
Purchase #2	$29.76	10.564%	$32.9038	$32.90	$32.90	$32.90
Purchase #3	$164.33	3.188%	$169.5688	$169.57	$169.55	$169.60
Purchase #4	$117.74	4.490%	$123.0265	$123.03	$123.05	$123.00
Purchase #5	$87.64	8.590%	$95.1683	$95.17	$95.15	$95.20
Purchase #6	$61.61	13.798%	$70.1109	$70.11	$70.10	$70.10
Purchase #7	$97.68	8.152%	$105.6429	$105.64	$105.65	$105.60
7 purchase totals =	$805.46		$860.7899	$860.79	$860.75	$860.80