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	$143.43	7.843%	$154.6792	$154.68	$154.70	$154.70
Purchase #2	$176.30	8.182%	$190.7249	$190.72	$190.70	$190.70
Purchase #3	$56.60	5.576%	$59.756	$59.76	$59.75	$59.80
Purchase #4	$112.76	5.805%	$119.3057	$119.31	$119.30	$119.30
Purchase #5	$164.62	10.117%	$181.2746	$181.27	$181.25	$181.30
Purchase #6	$187.95	11.409%	$209.3932	$209.39	$209.40	$209.40
Purchase #7	$197.70	9.342%	$216.1691	$216.17	$216.15	$216.20
7 purchase totals =	$1,039.36		$1,131.3027	$1,131.30	$1,131.25	$1,131.40