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	$239.39	6.626%	$255.252	$255.25	$255.25	$255.30
Purchase #2	$152.31	13.397%	$172.715	$172.72	$172.70	$172.70
Purchase #3	$139.71	5.208%	$146.9861	$146.99	$147.00	$147.00
Purchase #4	$123.76	6.227%	$131.4665	$131.47	$131.45	$131.50
Purchase #5	$178.69	8.255%	$193.4409	$193.44	$193.45	$193.40
Purchase #6	$201.52	5.132%	$211.862	$211.86	$211.85	$211.90
Purchase #7	$249.81	9.571%	$273.7193	$273.72	$273.70	$273.70
7 purchase totals =	$1,285.19		$1,385.4418	$1,385.45	$1,385.40	$1,385.50