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	$138.91	10.460%	$153.44	$153.44	$153.45	$153.40
Purchase #2	$100.26	10.865%	$111.1532	$111.15	$111.15	$111.20
Purchase #3	$25.31	5.674%	$26.7461	$26.75	$26.75	$26.70
Purchase #4	$78.29	13.430%	$88.8043	$88.80	$88.80	$88.80
Purchase #5	$236.67	11.237%	$263.2646	$263.26	$263.25	$263.30
Purchase #6	$52.74	11.802%	$58.9644	$58.96	$58.95	$59.00
Purchase #7	$104.25	7.311%	$111.8717	$111.87	$111.85	$111.90
7 purchase totals =	$736.43		$814.2443	$814.23	$814.20	$814.30