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	$222.72	13.805%	$253.4665	$253.47	$253.45	$253.50
Purchase #2	$52.54	12.748%	$59.2378	$59.24	$59.25	$59.20
Purchase #3	$214.70	9.222%	$234.4996	$234.50	$234.50	$234.50
Purchase #4	$82.99	10.379%	$91.6035	$91.60	$91.60	$91.60
Purchase #5	$195.86	10.263%	$215.9611	$215.96	$215.95	$216.00
Purchase #6	$50.47	11.448%	$56.2478	$56.25	$56.25	$56.20
Purchase #7	$155.67	10.802%	$172.4855	$172.49	$172.50	$172.50
7 purchase totals =	$974.95		$1,083.5018	$1,083.51	$1,083.50	$1,083.50