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	$32.47	3.558%	$33.6253	$33.63	$33.65	$33.60
Purchase #2	$215.32	4.392%	$224.7769	$224.78	$224.80	$224.80
Purchase #3	$240.90	13.268%	$272.8626	$272.86	$272.85	$272.90
Purchase #4	$156.93	8.724%	$170.6206	$170.62	$170.60	$170.60
Purchase #5	$20.50	5.154%	$21.5566	$21.56	$21.55	$21.60
Purchase #6	$213.55	4.567%	$223.3028	$223.30	$223.30	$223.30
Purchase #7	$54.64	9.283%	$59.7122	$59.71	$59.70	$59.70
7 purchase totals =	$934.31		$1,006.4570	$1,006.46	$1,006.45	$1,006.50