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	$204.98	9.214%	$223.8669	$223.87	$223.85	$223.90
Purchase #2	$160.30	11.467%	$178.6816	$178.68	$178.70	$178.70
Purchase #3	$83.38	8.242%	$90.2522	$90.25	$90.25	$90.30
Purchase #4	$55.38	7.365%	$59.4587	$59.46	$59.45	$59.50
Purchase #5	$180.55	10.359%	$199.2532	$199.25	$199.25	$199.30
Purchase #6	$243.70	10.542%	$269.3909	$269.39	$269.40	$269.40
Purchase #7	$153.95	10.822%	$170.6105	$170.61	$170.60	$170.60
7 purchase totals =	$1,082.24		$1,191.5140	$1,191.51	$1,191.50	$1,191.70