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	$131.34	10.114%	$144.6237	$144.62	$144.60	$144.60
Purchase #2	$88.63	5.863%	$93.8264	$93.83	$93.85	$93.80
Purchase #3	$82.95	8.406%	$89.9228	$89.92	$89.90	$89.90
Purchase #4	$133.84	5.652%	$141.4046	$141.40	$141.40	$141.40
Purchase #5	$156.52	11.590%	$174.6607	$174.66	$174.65	$174.70
Purchase #6	$199.65	5.595%	$210.8204	$210.82	$210.80	$210.80
Purchase #7	$148.78	3.288%	$153.6719	$153.67	$153.65	$153.70
7 purchase totals =	$941.71		$1,008.9305	$1,008.92	$1,008.85	$1,008.90