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	$82.37	10.155%	$90.7347	$90.73	$90.75	$90.70
Purchase #2	$77.83	10.607%	$86.0854	$86.09	$86.10	$86.10
Purchase #3	$57.67	13.307%	$65.3441	$65.34	$65.35	$65.30
Purchase #4	$217.72	3.184%	$224.6522	$224.65	$224.65	$224.70
Purchase #5	$76.76	8.249%	$83.0919	$83.09	$83.10	$83.10
Purchase #6	$193.25	3.207%	$199.4475	$199.45	$199.45	$199.40
Purchase #7	$234.35	11.569%	$261.462	$261.46	$261.45	$261.50
7 purchase totals =	$939.95		$1,010.8178	$1,010.81	$1,010.85	$1,010.80