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	$116.30	13.392%	$131.8749	$131.87	$131.85	$131.90
Purchase #2	$82.89	9.167%	$90.4885	$90.49	$90.50	$90.50
Purchase #3	$215.67	3.865%	$224.0056	$224.01	$224.00	$224.00
Purchase #4	$26.34	11.407%	$29.3446	$29.34	$29.35	$29.30
Purchase #5	$79.98	7.226%	$85.7594	$85.76	$85.75	$85.80
Purchase #6	$131.53	13.684%	$149.5286	$149.53	$149.55	$149.50
Purchase #7	$26.62	3.803%	$27.6324	$27.63	$27.65	$27.60
7 purchase totals =	$679.33		$738.6340	$738.63	$738.65	$738.60