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	$41.54	3.449%	$42.9727	$42.97	$42.95	$43.00
Purchase #2	$44.45	4.376%	$46.3951	$46.40	$46.40	$46.40
Purchase #3	$189.97	7.110%	$203.4769	$203.48	$203.50	$203.50
Purchase #4	$107.99	13.474%	$122.5406	$122.54	$122.55	$122.50
Purchase #5	$13.78	6.576%	$14.6862	$14.69	$14.70	$14.70
Purchase #6	$123.60	3.399%	$127.8012	$127.80	$127.80	$127.80
Purchase #7	$86.89	4.105%	$90.4568	$90.46	$90.45	$90.50
7 purchase totals =	$608.22		$648.3295	$648.34	$648.35	$648.40