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	$213.53	4.605%	$223.3631	$223.36	$223.35	$223.40
Purchase #2	$134.50	7.398%	$144.4503	$144.45	$144.45	$144.50
Purchase #3	$245.49	11.389%	$273.4489	$273.45	$273.45	$273.40
Purchase #4	$53.26	11.148%	$59.1974	$59.20	$59.20	$59.20
Purchase #5	$237.84	8.212%	$257.3714	$257.37	$257.35	$257.40
Purchase #6	$111.67	7.356%	$119.8844	$119.88	$119.90	$119.90
Purchase #7	$11.83	3.320%	$12.2228	$12.22	$12.20	$12.20
7 purchase totals =	$1,008.12		$1,089.9383	$1,089.93	$1,089.90	$1,090.00