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	$242.77	10.245%	$267.6418	$267.64	$267.65	$267.60
Purchase #2	$6.95	5.851%	$7.3566	$7.36	$7.35	$7.40
Purchase #3	$137.72	13.467%	$156.2668	$156.27	$156.25	$156.30
Purchase #4	$175.84	3.442%	$181.8924	$181.89	$181.90	$181.90
Purchase #5	$59.31	3.533%	$61.4054	$61.41	$61.40	$61.40
Purchase #6	$125.59	5.313%	$132.2626	$132.26	$132.25	$132.30
Purchase #7	$217.51	8.741%	$236.5225	$236.52	$236.50	$236.50
7 purchase totals =	$965.69		$1,043.3481	$1,043.35	$1,043.30	$1,043.40