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	$182.25	5.241%	$191.8017	$191.80	$191.80	$191.80
Purchase #2	$225.89	13.302%	$255.9379	$255.94	$255.95	$255.90
Purchase #3	$50.53	11.844%	$56.5148	$56.51	$56.50	$56.50
Purchase #4	$189.58	5.267%	$199.5652	$199.57	$199.55	$199.60
Purchase #5	$95.42	4.583%	$99.7931	$99.79	$99.80	$99.80
Purchase #6	$46.34	13.622%	$52.6524	$52.65	$52.65	$52.70
Purchase #7	$67.36	13.653%	$76.5567	$76.56	$76.55	$76.60
7 purchase totals =	$857.37		$932.8218	$932.82	$932.80	$932.90