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	$202.61	4.542%	$211.8125	$211.81	$211.80	$211.80
Purchase #2	$73.77	10.730%	$81.6855	$81.69	$81.70	$81.70
Purchase #3	$9.65	10.692%	$10.6818	$10.68	$10.70	$10.70
Purchase #4	$131.46	6.414%	$139.8918	$139.89	$139.90	$139.90
Purchase #5	$188.73	5.620%	$199.3366	$199.34	$199.35	$199.30
Purchase #6	$231.92	10.738%	$256.8236	$256.82	$256.80	$256.80
Purchase #7	$36.49	10.359%	$40.27	$40.27	$40.25	$40.30
7 purchase totals =	$874.63		$940.5018	$940.50	$940.50	$940.50