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	$38.48	11.867%	$43.0464	$43.05	$43.05	$43.00
Purchase #2	$219.44	6.124%	$232.8785	$232.88	$232.90	$232.90
Purchase #3	$209.49	3.794%	$217.4381	$217.44	$217.45	$217.40
Purchase #4	$40.49	13.321%	$45.8837	$45.88	$45.90	$45.90
Purchase #5	$202.83	4.630%	$212.221	$212.22	$212.20	$212.20
Purchase #6	$24.33	11.167%	$27.0469	$27.05	$27.05	$27.00
Purchase #7	$78.83	4.434%	$82.3253	$82.33	$82.35	$82.30
7 purchase totals =	$813.89		$860.8399	$860.85	$860.90	$860.70