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	$114.82	9.223%	$125.4098	$125.41	$125.40	$125.40
Purchase #2	$176.97	11.233%	$196.849	$196.85	$196.85	$196.80
Purchase #3	$224.55	10.720%	$248.6218	$248.62	$248.60	$248.60
Purchase #4	$158.25	10.388%	$174.689	$174.69	$174.70	$174.70
Purchase #5	$68.57	13.814%	$78.0423	$78.04	$78.05	$78.00
Purchase #6	$48.54	7.365%	$52.115	$52.12	$52.10	$52.10
Purchase #7	$15.35	12.769%	$17.31	$17.31	$17.30	$17.30
7 purchase totals =	$807.05		$893.0369	$893.04	$893.00	$892.90