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	$78.29	6.597%	$83.4548	$83.45	$83.45	$83.50
Purchase #2	$31.55	8.185%	$34.1324	$34.13	$34.15	$34.10
Purchase #3	$6.66	12.137%	$7.4683	$7.47	$7.45	$7.50
Purchase #4	$230.57	10.776%	$255.4162	$255.42	$255.40	$255.40
Purchase #5	$71.61	6.859%	$76.5217	$76.52	$76.50	$76.50
Purchase #6	$53.34	9.648%	$58.4862	$58.49	$58.50	$58.50
Purchase #7	$197.91	6.526%	$210.8256	$210.83	$210.85	$210.80
7 purchase totals =	$669.93		$726.3052	$726.31	$726.30	$726.30