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	$199.47	10.245%	$219.9057	$219.91	$219.90	$219.90
Purchase #2	$200.33	12.430%	$225.231	$225.23	$225.25	$225.20
Purchase #3	$61.79	8.118%	$66.8061	$66.81	$66.80	$66.80
Purchase #4	$141.36	4.837%	$148.1976	$148.20	$148.20	$148.20
Purchase #5	$32.83	6.616%	$35.002	$35.00	$35.00	$35.00
Purchase #6	$55.51	3.216%	$57.2952	$57.30	$57.30	$57.30
Purchase #7	$53.60	11.607%	$59.8214	$59.82	$59.80	$59.80
7 purchase totals =	$744.89		$812.2590	$812.27	$812.25	$812.20