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	$132.82	10.263%	$146.4513	$146.45	$146.45	$146.50
Purchase #2	$27.82	7.598%	$29.9338	$29.93	$29.95	$29.90
Purchase #3	$79.85	12.580%	$89.8951	$89.90	$89.90	$89.90
Purchase #4	$55.37	10.775%	$61.3361	$61.34	$61.35	$61.30
Purchase #5	$126.48	4.706%	$132.4321	$132.43	$132.45	$132.40
Purchase #6	$56.42	5.575%	$59.5654	$59.57	$59.55	$59.60
Purchase #7	$216.90	4.664%	$227.0162	$227.02	$227.00	$227.00
7 purchase totals =	$695.66		$746.6300	$746.64	$746.65	$746.60