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	$22.57	3.171%	$23.2857	$23.29	$23.30	$23.30
Purchase #2	$109.60	9.120%	$119.5955	$119.60	$119.60	$119.60
Purchase #3	$231.43	11.827%	$258.8012	$258.80	$258.80	$258.80
Purchase #4	$215.49	3.382%	$222.7779	$222.78	$222.80	$222.80
Purchase #5	$164.64	11.817%	$184.0955	$184.10	$184.10	$184.10
Purchase #6	$136.36	4.729%	$142.8085	$142.81	$142.80	$142.80
Purchase #7	$75.60	4.259%	$78.8198	$78.82	$78.80	$78.80
7 purchase totals =	$955.69		$1,030.1841	$1,030.20	$1,030.20	$1,030.20