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	$225.75	13.332%	$255.847	$255.85	$255.85	$255.80
Purchase #2	$176.57	10.417%	$194.9633	$194.96	$194.95	$195.00
Purchase #3	$13.47	6.425%	$14.3354	$14.34	$14.35	$14.30
Purchase #4	$66.73	8.647%	$72.5001	$72.50	$72.50	$72.50
Purchase #5	$39.95	7.801%	$43.0665	$43.07	$43.05	$43.10
Purchase #6	$229.71	3.441%	$237.6143	$237.61	$237.60	$237.60
Purchase #7	$248.79	7.516%	$267.4891	$267.49	$267.50	$267.50
7 purchase totals =	$1,000.97		$1,085.8157	$1,085.82	$1,085.80	$1,085.80