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	$40.89	10.535%	$45.1978	$45.20	$45.20	$45.20
Purchase #2	$37.66	10.604%	$41.6535	$41.65	$41.65	$41.70
Purchase #3	$108.45	5.539%	$114.457	$114.46	$114.45	$114.50
Purchase #4	$43.57	13.733%	$49.5535	$49.55	$49.55	$49.60
Purchase #5	$156.31	8.601%	$169.7542	$169.75	$169.75	$169.80
Purchase #6	$141.42	10.187%	$155.8265	$155.83	$155.85	$155.80
Purchase #7	$172.59	11.815%	$192.9815	$192.98	$193.00	$193.00
7 purchase totals =	$700.89		$769.4240	$769.42	$769.45	$769.60