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	$42.78	3.382%	$44.2268	$44.23	$44.25	$44.20
Purchase #2	$28.29	12.437%	$31.8084	$31.81	$31.80	$31.80
Purchase #3	$12.67	7.549%	$13.6265	$13.63	$13.65	$13.60
Purchase #4	$129.40	11.640%	$144.4622	$144.46	$144.45	$144.50
Purchase #5	$180.93	10.419%	$199.7811	$199.78	$199.80	$199.80
Purchase #6	$67.87	11.204%	$75.4742	$75.47	$75.45	$75.50
Purchase #7	$39.37	8.656%	$42.7779	$42.78	$42.80	$42.80
7 purchase totals =	$501.31		$552.1571	$552.16	$552.20	$552.20