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	$154.33	7.294%	$165.5868	$165.59	$165.60	$165.60
Purchase #2	$134.46	13.277%	$152.3123	$152.31	$152.30	$152.30
Purchase #3	$30.69	11.433%	$34.1988	$34.20	$34.20	$34.20
Purchase #4	$100.58	5.139%	$105.7488	$105.75	$105.75	$105.70
Purchase #5	$199.61	4.436%	$208.4647	$208.46	$208.45	$208.50
Purchase #6	$227.36	13.417%	$257.8649	$257.86	$257.85	$257.90
Purchase #7	$173.94	3.117%	$179.3617	$179.36	$179.35	$179.40
7 purchase totals =	$1,020.97		$1,103.5380	$1,103.53	$1,103.50	$1,103.60