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	$229.38	7.437%	$246.439	$246.44	$246.45	$246.40
Purchase #2	$228.56	11.123%	$253.9827	$253.98	$254.00	$254.00
Purchase #3	$58.78	13.381%	$66.6454	$66.65	$66.65	$66.60
Purchase #4	$243.85	4.374%	$254.516	$254.52	$254.50	$254.50
Purchase #5	$96.55	10.716%	$106.8963	$106.90	$106.90	$106.90
Purchase #6	$140.67	10.282%	$155.1337	$155.13	$155.15	$155.10
Purchase #7	$78.68	4.863%	$82.5062	$82.51	$82.50	$82.50
7 purchase totals =	$1,076.47		$1,166.1193	$1,166.13	$1,166.15	$1,166.00