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	$216.41	12.133%	$242.667	$242.67	$242.65	$242.70
Purchase #2	$49.48	10.273%	$54.5631	$54.56	$54.55	$54.60
Purchase #3	$110.91	6.196%	$117.782	$117.78	$117.80	$117.80
Purchase #4	$192.47	7.106%	$206.1469	$206.15	$206.15	$206.10
Purchase #5	$248.69	5.712%	$262.8952	$262.90	$262.90	$262.90
Purchase #6	$113.51	4.333%	$118.4284	$118.43	$118.45	$118.40
Purchase #7	$48.96	7.806%	$52.7818	$52.78	$52.80	$52.80
7 purchase totals =	$980.43		$1,055.2644	$1,055.27	$1,055.30	$1,055.30