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	$112.84	12.442%	$126.8796	$126.88	$126.90	$126.90
Purchase #2	$156.44	6.192%	$166.1268	$166.13	$166.15	$166.10
Purchase #3	$128.55	4.120%	$133.8463	$133.85	$133.85	$133.80
Purchase #4	$32.77	12.778%	$36.9574	$36.96	$36.95	$37.00
Purchase #5	$54.33	5.779%	$57.4697	$57.47	$57.45	$57.50
Purchase #6	$83.56	9.772%	$91.7255	$91.73	$91.75	$91.70
Purchase #7	$230.79	10.705%	$255.4961	$255.50	$255.50	$255.50
7 purchase totals =	$799.28		$868.5014	$868.52	$868.55	$868.50