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	$137.75	13.746%	$156.6851	$156.69	$156.70	$156.70
Purchase #2	$42.81	7.451%	$45.9998	$46.00	$46.00	$46.00
Purchase #3	$116.30	10.520%	$128.5348	$128.53	$128.55	$128.50
Purchase #4	$215.34	3.256%	$222.3515	$222.35	$222.35	$222.40
Purchase #5	$233.47	6.330%	$248.2487	$248.25	$248.25	$248.20
Purchase #6	$164.59	12.145%	$184.5795	$184.58	$184.60	$184.60
Purchase #7	$222.31	12.715%	$250.5767	$250.58	$250.60	$250.60
7 purchase totals =	$1,132.57		$1,236.9761	$1,236.98	$1,237.05	$1,237.00