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	$234.45	4.846%	$245.8114	$245.81	$245.80	$245.80
Purchase #2	$116.51	13.522%	$132.2645	$132.26	$132.25	$132.30
Purchase #3	$156.89	11.243%	$174.5291	$174.53	$174.55	$174.50
Purchase #4	$89.33	3.369%	$92.3395	$92.34	$92.35	$92.30
Purchase #5	$204.50	6.522%	$217.8375	$217.84	$217.85	$217.80
Purchase #6	$247.90	5.753%	$262.1617	$262.16	$262.15	$262.20
Purchase #7	$243.57	6.156%	$258.5642	$258.56	$258.55	$258.60
7 purchase totals =	$1,293.15		$1,383.5079	$1,383.50	$1,383.50	$1,383.50