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	$227.73	12.145%	$255.3878	$255.39	$255.40	$255.40
Purchase #2	$69.77	4.311%	$72.7778	$72.78	$72.80	$72.80
Purchase #3	$172.26	13.650%	$195.7735	$195.77	$195.75	$195.80
Purchase #4	$13.86	5.524%	$14.6256	$14.63	$14.65	$14.60
Purchase #5	$172.71	10.604%	$191.0242	$191.02	$191.00	$191.00
Purchase #6	$243.88	3.538%	$252.5085	$252.51	$252.50	$252.50
Purchase #7	$38.53	4.699%	$40.3405	$40.34	$40.35	$40.30
7 purchase totals =	$938.74		$1,022.4379	$1,022.44	$1,022.45	$1,022.40