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	$99.36	6.179%	$105.4995	$105.50	$105.50	$105.50
Purchase #2	$10.76	13.537%	$12.2166	$12.22	$12.20	$12.20
Purchase #3	$73.87	6.703%	$78.8215	$78.82	$78.80	$78.80
Purchase #4	$216.71	9.366%	$237.0071	$237.01	$237.00	$237.00
Purchase #5	$137.39	10.552%	$151.8874	$151.89	$151.90	$151.90
Purchase #6	$117.85	10.813%	$130.5931	$130.59	$130.60	$130.60
Purchase #7	$203.28	11.106%	$225.8563	$225.86	$225.85	$225.90
7 purchase totals =	$859.22		$941.8815	$941.89	$941.85	$941.90