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	$191.37	4.717%	$200.3969	$200.40	$200.40	$200.40
Purchase #2	$144.38	4.790%	$151.2958	$151.30	$151.30	$151.30
Purchase #3	$158.34	8.714%	$172.1377	$172.14	$172.15	$172.10
Purchase #4	$93.86	8.631%	$101.9611	$101.96	$101.95	$102.00
Purchase #5	$16.44	10.413%	$18.1519	$18.15	$18.15	$18.20
Purchase #6	$228.60	12.381%	$256.903	$256.90	$256.90	$256.90
Purchase #7	$108.78	12.446%	$122.3188	$122.32	$122.30	$122.30
7 purchase totals =	$941.77		$1,023.1652	$1,023.17	$1,023.15	$1,023.20