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	$104.34	6.837%	$111.4737	$111.47	$111.45	$111.50
Purchase #2	$226.88	3.486%	$234.789	$234.79	$234.80	$234.80
Purchase #3	$134.66	5.408%	$141.9424	$141.94	$141.95	$141.90
Purchase #4	$36.53	13.794%	$41.5689	$41.57	$41.55	$41.60
Purchase #5	$189.86	5.162%	$199.6606	$199.66	$199.65	$199.70
Purchase #6	$40.96	11.585%	$45.7052	$45.71	$45.70	$45.70
Purchase #7	$228.85	6.577%	$243.9015	$243.90	$243.90	$243.90
7 purchase totals =	$962.08		$1,019.0413	$1,019.04	$1,019.00	$1,019.10