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	$131.45	7.154%	$140.8539	$140.85	$140.85	$140.90
Purchase #2	$79.29	12.508%	$89.2076	$89.21	$89.20	$89.20
Purchase #3	$139.85	12.118%	$156.797	$156.80	$156.80	$156.80
Purchase #4	$236.71	3.142%	$244.1474	$244.15	$244.15	$244.10
Purchase #5	$208.52	4.471%	$217.8429	$217.84	$217.85	$217.80
Purchase #6	$95.76	13.166%	$108.3678	$108.37	$108.35	$108.40
Purchase #7	$110.38	8.267%	$119.5051	$119.51	$119.50	$119.50
7 purchase totals =	$1,001.96		$1,076.7217	$1,076.73	$1,076.70	$1,076.70