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	$33.77	10.342%	$37.2625	$37.26	$37.25	$37.30
Purchase #2	$28.64	13.300%	$32.4491	$32.45	$32.45	$32.40
Purchase #3	$190.52	5.390%	$200.789	$200.79	$200.80	$200.80
Purchase #4	$195.81	11.295%	$217.9267	$217.93	$217.95	$217.90
Purchase #5	$47.76	4.792%	$50.0487	$50.05	$50.05	$50.00
Purchase #6	$181.39	7.709%	$195.3734	$195.37	$195.35	$195.40
Purchase #7	$131.45	8.794%	$143.0097	$143.01	$143.00	$143.00
7 purchase totals =	$809.34		$876.8591	$876.86	$876.85	$876.80