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	$109.47	6.287%	$116.3524	$116.35	$116.35	$116.40
Purchase #2	$131.51	4.143%	$136.9585	$136.96	$136.95	$137.00
Purchase #3	$78.33	5.450%	$82.599	$82.60	$82.60	$82.60
Purchase #4	$137.43	5.418%	$144.876	$144.88	$144.90	$144.90
Purchase #5	$142.98	10.434%	$157.8985	$157.90	$157.90	$157.90
Purchase #6	$42.27	8.488%	$45.8579	$45.86	$45.85	$45.90
Purchase #7	$238.60	10.361%	$263.3213	$263.32	$263.30	$263.30
7 purchase totals =	$880.59		$947.8636	$947.87	$947.85	$948.00