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	$26.63	3.533%	$27.5708	$27.57	$27.55	$27.60
Purchase #2	$211.98	8.863%	$230.7678	$230.77	$230.75	$230.80
Purchase #3	$70.61	11.232%	$78.5409	$78.54	$78.55	$78.50
Purchase #4	$159.94	7.783%	$172.3881	$172.39	$172.40	$172.40
Purchase #5	$192.46	5.595%	$203.2281	$203.23	$203.25	$203.20
Purchase #6	$75.73	13.358%	$85.846	$85.85	$85.85	$85.80
Purchase #7	$210.63	11.114%	$234.0394	$234.04	$234.05	$234.00
7 purchase totals =	$947.98		$1,032.3811	$1,032.39	$1,032.40	$1,032.30