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	$234.35	9.543%	$256.714	$256.71	$256.70	$256.70
Purchase #2	$140.44	7.448%	$150.9	$150.90	$150.90	$150.90
Purchase #3	$79.26	5.818%	$83.8713	$83.87	$83.85	$83.90
Purchase #4	$55.44	7.522%	$59.6102	$59.61	$59.60	$59.60
Purchase #5	$235.59	8.636%	$255.9356	$255.94	$255.95	$255.90
Purchase #6	$22.92	3.113%	$23.6335	$23.63	$23.65	$23.60
Purchase #7	$190.47	9.214%	$208.0199	$208.02	$208.00	$208.00
7 purchase totals =	$958.47		$1,038.6845	$1,038.68	$1,038.65	$1,038.60