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	$224.88	8.340%	$243.635	$243.64	$243.65	$243.60
Purchase #2	$245.28	13.294%	$277.8875	$277.89	$277.90	$277.90
Purchase #3	$206.83	8.570%	$224.5553	$224.56	$224.55	$224.60
Purchase #4	$212.94	4.528%	$222.5819	$222.58	$222.60	$222.60
Purchase #5	$215.27	12.863%	$242.9602	$242.96	$242.95	$243.00
Purchase #6	$64.33	11.629%	$71.8109	$71.81	$71.80	$71.80
Purchase #7	$227.47	12.787%	$256.5566	$256.56	$256.55	$256.60
7 purchase totals =	$1,397.00		$1,539.9874	$1,540.00	$1,540.00	$1,540.10