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	$79.88	6.770%	$85.2879	$85.29	$85.30	$85.30
Purchase #2	$160.37	5.360%	$168.9658	$168.97	$168.95	$169.00
Purchase #3	$101.38	10.249%	$111.7704	$111.77	$111.75	$111.80
Purchase #4	$130.83	4.353%	$136.525	$136.53	$136.55	$136.50
Purchase #5	$162.42	4.167%	$169.188	$169.19	$169.20	$169.20
Purchase #6	$225.47	12.250%	$253.0901	$253.09	$253.10	$253.10
Purchase #7	$214.34	3.183%	$221.1624	$221.16	$221.15	$221.20
7 purchase totals =	$1,074.69		$1,145.9896	$1,146.00	$1,146.00	$1,146.10