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	$236.34	9.493%	$258.7758	$258.78	$258.80	$258.80
Purchase #2	$39.52	3.382%	$40.8566	$40.86	$40.85	$40.90
Purchase #3	$196.62	6.238%	$208.8852	$208.89	$208.90	$208.90
Purchase #4	$223.53	7.743%	$240.8379	$240.84	$240.85	$240.80
Purchase #5	$39.31	6.766%	$41.9697	$41.97	$41.95	$42.00
Purchase #6	$167.90	8.803%	$182.6802	$182.68	$182.70	$182.70
Purchase #7	$160.59	7.598%	$172.7916	$172.79	$172.80	$172.80
7 purchase totals =	$1,063.81		$1,146.7970	$1,146.81	$1,146.85	$1,146.90