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	$182.85	12.563%	$205.8214	$205.82	$205.80	$205.80
Purchase #2	$82.60	6.679%	$88.1169	$88.12	$88.10	$88.10
Purchase #3	$137.78	12.669%	$155.2353	$155.24	$155.25	$155.20
Purchase #4	$89.72	11.427%	$99.9723	$99.97	$99.95	$100.00
Purchase #5	$85.96	10.798%	$95.242	$95.24	$95.25	$95.20
Purchase #6	$59.75	10.107%	$65.7889	$65.79	$65.80	$65.80
Purchase #7	$223.76	7.549%	$240.6516	$240.65	$240.65	$240.70
7 purchase totals =	$862.42		$950.8284	$950.83	$950.80	$950.80