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	$139.67	13.249%	$158.1749	$158.17	$158.15	$158.20
Purchase #2	$149.64	7.377%	$160.6789	$160.68	$160.70	$160.70
Purchase #3	$171.77	4.262%	$179.0908	$179.09	$179.10	$179.10
Purchase #4	$148.29	4.608%	$155.1232	$155.12	$155.10	$155.10
Purchase #5	$202.89	3.457%	$209.9039	$209.90	$209.90	$209.90
Purchase #6	$125.84	13.218%	$142.4735	$142.47	$142.45	$142.50
Purchase #7	$128.28	6.559%	$136.6939	$136.69	$136.70	$136.70
7 purchase totals =	$1,066.38		$1,142.1391	$1,142.12	$1,142.10	$1,142.20