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	$32.74	4.423%	$34.1881	$34.19	$34.20	$34.20
Purchase #2	$240.75	6.180%	$255.6284	$255.63	$255.65	$255.60
Purchase #3	$125.71	5.852%	$133.0665	$133.07	$133.05	$133.10
Purchase #4	$141.27	3.753%	$146.5719	$146.57	$146.55	$146.60
Purchase #5	$193.30	13.241%	$218.8949	$218.89	$218.90	$218.90
Purchase #6	$172.53	10.392%	$190.4593	$190.46	$190.45	$190.50
Purchase #7	$80.35	3.871%	$83.4603	$83.46	$83.45	$83.50
7 purchase totals =	$986.65		$1,062.2694	$1,062.27	$1,062.25	$1,062.40