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	$139.88	7.327%	$150.129	$150.13	$150.15	$150.10
Purchase #2	$32.80	13.218%	$37.1355	$37.14	$37.15	$37.10
Purchase #3	$106.78	10.217%	$117.6897	$117.69	$117.70	$117.70
Purchase #4	$139.36	13.811%	$158.607	$158.61	$158.60	$158.60
Purchase #5	$67.92	5.750%	$71.8254	$71.83	$71.85	$71.80
Purchase #6	$86.60	3.706%	$89.8094	$89.81	$89.80	$89.80
Purchase #7	$82.98	13.372%	$94.0761	$94.08	$94.10	$94.10
7 purchase totals =	$656.32		$719.2721	$719.29	$719.35	$719.20