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	$205.30	6.446%	$218.5336	$218.53	$218.55	$218.50
Purchase #2	$83.70	7.638%	$90.093	$90.09	$90.10	$90.10
Purchase #3	$185.32	12.646%	$208.7556	$208.76	$208.75	$208.80
Purchase #4	$57.83	6.532%	$61.6075	$61.61	$61.60	$61.60
Purchase #5	$212.62	8.453%	$230.5928	$230.59	$230.60	$230.60
Purchase #6	$17.90	11.806%	$20.0133	$20.01	$20.00	$20.00
Purchase #7	$200.90	6.571%	$214.1011	$214.10	$214.10	$214.10
7 purchase totals =	$963.57		$1,043.6969	$1,043.69	$1,043.70	$1,043.70