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	$129.47	11.870%	$144.8381	$144.84	$144.85	$144.80
Purchase #2	$89.53	5.161%	$94.1506	$94.15	$94.15	$94.20
Purchase #3	$247.59	3.788%	$256.9687	$256.97	$256.95	$257.00
Purchase #4	$131.25	11.345%	$146.1403	$146.14	$146.15	$146.10
Purchase #5	$99.70	10.829%	$110.4965	$110.50	$110.50	$110.50
Purchase #6	$201.39	10.625%	$222.7877	$222.79	$222.80	$222.80
Purchase #7	$136.42	3.487%	$141.177	$141.18	$141.20	$141.20
7 purchase totals =	$1,035.35		$1,116.5589	$1,116.57	$1,116.60	$1,116.60