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	$130.70	12.164%	$146.5983	$146.60	$146.60	$146.60
Purchase #2	$162.67	13.725%	$184.9965	$185.00	$185.00	$185.00
Purchase #3	$118.67	9.289%	$129.6933	$129.69	$129.70	$129.70
Purchase #4	$132.85	6.428%	$141.3896	$141.39	$141.40	$141.40
Purchase #5	$123.78	5.412%	$130.479	$130.48	$130.50	$130.50
Purchase #6	$111.75	6.820%	$119.3714	$119.37	$119.35	$119.40
Purchase #7	$217.42	5.381%	$229.1194	$229.12	$229.10	$229.10
7 purchase totals =	$997.84		$1,081.6475	$1,081.65	$1,081.65	$1,081.70