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	$141.46	11.411%	$157.602	$157.60	$157.60	$157.60
Purchase #2	$53.46	8.300%	$57.8972	$57.90	$57.90	$57.90
Purchase #3	$177.47	8.103%	$191.8504	$191.85	$191.85	$191.90
Purchase #4	$75.76	9.244%	$82.7633	$82.76	$82.75	$82.80
Purchase #5	$86.57	12.570%	$97.4518	$97.45	$97.45	$97.50
Purchase #6	$218.27	11.237%	$242.797	$242.80	$242.80	$242.80
Purchase #7	$118.89	12.806%	$134.1151	$134.12	$134.10	$134.10
7 purchase totals =	$871.88		$964.4768	$964.48	$964.45	$964.60