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	$95.61	3.792%	$99.2355	$99.24	$99.25	$99.20
Purchase #2	$114.50	13.859%	$130.3686	$130.37	$130.35	$130.40
Purchase #3	$42.90	12.755%	$48.3719	$48.37	$48.35	$48.40
Purchase #4	$179.30	6.537%	$191.0208	$191.02	$191.00	$191.00
Purchase #5	$173.91	13.104%	$196.6992	$196.70	$196.70	$196.70
Purchase #6	$240.65	6.276%	$255.7532	$255.75	$255.75	$255.80
Purchase #7	$108.41	12.788%	$122.2735	$122.27	$122.25	$122.30
7 purchase totals =	$955.28		$1,043.7227	$1,043.72	$1,043.65	$1,043.80