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	$26.61	12.521%	$29.9418	$29.94	$29.95	$29.90
Purchase #2	$206.59	5.870%	$218.7168	$218.72	$218.70	$218.70
Purchase #3	$243.63	8.472%	$264.2703	$264.27	$264.25	$264.30
Purchase #4	$149.67	9.665%	$164.1356	$164.14	$164.15	$164.10
Purchase #5	$211.85	10.170%	$233.3951	$233.40	$233.40	$233.40
Purchase #6	$166.54	4.503%	$174.0393	$174.04	$174.05	$174.00
Purchase #7	$248.96	10.433%	$274.934	$274.93	$274.95	$274.90
7 purchase totals =	$1,253.85		$1,359.4329	$1,359.44	$1,359.45	$1,359.30