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	$222.83	10.607%	$246.4656	$246.47	$246.45	$246.50
Purchase #2	$127.89	13.547%	$145.2153	$145.22	$145.20	$145.20
Purchase #3	$83.34	10.637%	$92.2049	$92.20	$92.20	$92.20
Purchase #4	$184.25	3.365%	$190.45	$190.45	$190.45	$190.50
Purchase #5	$184.43	13.510%	$209.3465	$209.35	$209.35	$209.30
Purchase #6	$118.58	12.257%	$133.1144	$133.11	$133.10	$133.10
Purchase #7	$36.68	7.680%	$39.497	$39.50	$39.50	$39.50
7 purchase totals =	$958.00		$1,056.2937	$1,056.30	$1,056.25	$1,056.30