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	$209.61	10.777%	$232.1997	$232.20	$232.20	$232.20
Purchase #2	$64.60	8.191%	$69.8914	$69.89	$69.90	$69.90
Purchase #3	$99.66	11.650%	$111.2704	$111.27	$111.25	$111.30
Purchase #4	$32.81	6.369%	$34.8997	$34.90	$34.90	$34.90
Purchase #5	$159.74	6.657%	$170.3739	$170.37	$170.35	$170.40
Purchase #6	$93.62	10.697%	$103.6345	$103.63	$103.65	$103.60
Purchase #7	$127.38	13.732%	$144.8718	$144.87	$144.85	$144.90
7 purchase totals =	$787.42		$867.1414	$867.13	$867.10	$867.20