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	$210.77	4.130%	$219.4748	$219.47	$219.45	$219.50
Purchase #2	$84.55	7.172%	$90.6139	$90.61	$90.60	$90.60
Purchase #3	$82.44	10.252%	$90.8917	$90.89	$90.90	$90.90
Purchase #4	$90.35	10.401%	$99.7473	$99.75	$99.75	$99.70
Purchase #5	$195.29	10.687%	$216.1606	$216.16	$216.15	$216.20
Purchase #6	$194.46	10.648%	$215.1661	$215.17	$215.15	$215.20
Purchase #7	$234.51	5.750%	$247.9943	$247.99	$248.00	$248.00
7 purchase totals =	$1,092.37		$1,180.0487	$1,180.04	$1,180.00	$1,180.10