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	$236.94	13.842%	$269.7372	$269.74	$269.75	$269.70
Purchase #2	$71.95	5.774%	$76.1044	$76.10	$76.10	$76.10
Purchase #3	$40.72	3.730%	$42.2389	$42.24	$42.25	$42.20
Purchase #4	$65.27	10.422%	$72.0724	$72.07	$72.05	$72.10
Purchase #5	$110.74	8.873%	$120.566	$120.57	$120.55	$120.60
Purchase #6	$78.88	13.447%	$89.487	$89.49	$89.50	$89.50
Purchase #7	$175.96	12.530%	$198.0078	$198.01	$198.00	$198.00
7 purchase totals =	$780.46		$868.2137	$868.22	$868.20	$868.20