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	$33.29	3.498%	$34.4545	$34.45	$34.45	$34.50
Purchase #2	$135.77	6.394%	$144.4511	$144.45	$144.45	$144.50
Purchase #3	$213.71	12.523%	$240.4729	$240.47	$240.45	$240.50
Purchase #4	$209.32	6.119%	$222.1283	$222.13	$222.15	$222.10
Purchase #5	$26.46	5.201%	$27.8362	$27.84	$27.85	$27.80
Purchase #6	$187.50	3.407%	$193.8881	$193.89	$193.90	$193.90
Purchase #7	$60.89	9.245%	$66.5193	$66.52	$66.50	$66.50
7 purchase totals =	$866.94		$929.7504	$929.75	$929.75	$929.80