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	$69.86	3.799%	$72.514	$72.51	$72.50	$72.50
Purchase #2	$68.32	3.152%	$70.4734	$70.47	$70.45	$70.50
Purchase #3	$6.90	3.309%	$7.1283	$7.13	$7.15	$7.10
Purchase #4	$186.52	3.166%	$192.4252	$192.43	$192.45	$192.40
Purchase #5	$132.77	4.834%	$139.1881	$139.19	$139.20	$139.20
Purchase #6	$44.48	11.248%	$49.4831	$49.48	$49.50	$49.50
Purchase #7	$174.77	7.827%	$188.4492	$188.45	$188.45	$188.40
7 purchase totals =	$683.62		$719.6613	$719.66	$719.70	$719.60