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	$196.90	13.209%	$222.9085	$222.91	$222.90	$222.90
Purchase #2	$104.98	6.507%	$111.811	$111.81	$111.80	$111.80
Purchase #3	$161.38	7.480%	$173.4512	$173.45	$173.45	$173.50
Purchase #4	$142.77	9.217%	$155.9291	$155.93	$155.95	$155.90
Purchase #5	$102.46	5.701%	$108.3012	$108.30	$108.30	$108.30
Purchase #6	$158.95	8.660%	$172.7151	$172.72	$172.70	$172.70
Purchase #7	$28.34	10.546%	$31.3287	$31.33	$31.35	$31.30
7 purchase totals =	$895.78		$976.4448	$976.45	$976.45	$976.40