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	$65.27	12.296%	$73.2956	$73.30	$73.30	$73.30
Purchase #2	$32.28	4.757%	$33.8156	$33.82	$33.80	$33.80
Purchase #3	$60.66	3.604%	$62.8462	$62.85	$62.85	$62.80
Purchase #4	$42.49	11.576%	$47.4086	$47.41	$47.40	$47.40
Purchase #5	$75.35	11.382%	$83.9263	$83.93	$83.95	$83.90
Purchase #6	$190.67	3.110%	$196.5998	$196.60	$196.60	$196.60
Purchase #7	$227.80	8.458%	$247.0673	$247.07	$247.05	$247.10
7 purchase totals =	$694.52		$744.9594	$744.98	$744.95	$744.90