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	$230.82	10.427%	$254.8876	$254.89	$254.90	$254.90
Purchase #2	$243.70	5.317%	$256.6575	$256.66	$256.65	$256.70
Purchase #3	$238.92	6.874%	$255.3434	$255.34	$255.35	$255.30
Purchase #4	$152.52	8.616%	$165.6611	$165.66	$165.65	$165.70
Purchase #5	$198.86	7.562%	$213.8978	$213.90	$213.90	$213.90
Purchase #6	$184.72	9.656%	$202.5566	$202.56	$202.55	$202.60
Purchase #7	$37.52	5.153%	$39.4534	$39.45	$39.45	$39.50
7 purchase totals =	$1,287.06		$1,388.4574	$1,388.46	$1,388.45	$1,388.60