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	$97.42	4.121%	$101.4347	$101.43	$101.45	$101.40
Purchase #2	$193.88	13.373%	$219.8076	$219.81	$219.80	$219.80
Purchase #3	$6.73	11.181%	$7.4825	$7.48	$7.50	$7.50
Purchase #4	$160.78	6.161%	$170.6857	$170.69	$170.70	$170.70
Purchase #5	$204.96	10.779%	$227.0526	$227.05	$227.05	$227.10
Purchase #6	$225.49	13.788%	$256.5806	$256.58	$256.60	$256.60
Purchase #7	$162.94	3.130%	$168.04	$168.04	$168.05	$168.00
7 purchase totals =	$1,052.20		$1,151.0837	$1,151.08	$1,151.15	$1,151.10