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	$157.67	8.628%	$171.2738	$171.27	$171.25	$171.30
Purchase #2	$203.35	12.442%	$228.6508	$228.65	$228.65	$228.70
Purchase #3	$15.26	7.286%	$16.3718	$16.37	$16.35	$16.40
Purchase #4	$212.29	7.780%	$228.8062	$228.81	$228.80	$228.80
Purchase #5	$82.54	10.119%	$90.8922	$90.89	$90.90	$90.90
Purchase #6	$101.44	9.730%	$111.3101	$111.31	$111.30	$111.30
Purchase #7	$88.43	6.648%	$94.3088	$94.31	$94.30	$94.30
7 purchase totals =	$860.98		$941.6137	$941.61	$941.55	$941.70