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	$246.36	11.152%	$273.8341	$273.83	$273.85	$273.80
Purchase #2	$34.32	5.831%	$36.3212	$36.32	$36.30	$36.30
Purchase #3	$99.59	13.143%	$112.6791	$112.68	$112.70	$112.70
Purchase #4	$120.32	4.393%	$125.6057	$125.61	$125.60	$125.60
Purchase #5	$69.29	10.364%	$76.4712	$76.47	$76.45	$76.50
Purchase #6	$99.36	6.514%	$105.8323	$105.83	$105.85	$105.80
Purchase #7	$83.94	11.705%	$93.7652	$93.77	$93.75	$93.80
7 purchase totals =	$753.18		$824.5088	$824.51	$824.50	$824.50