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	$250.44	12.381%	$281.447	$281.45	$281.45	$281.40
Purchase #2	$119.50	13.837%	$136.0352	$136.04	$136.05	$136.00
Purchase #3	$243.83	8.194%	$263.8094	$263.81	$263.80	$263.80
Purchase #4	$155.66	3.354%	$160.8808	$160.88	$160.90	$160.90
Purchase #5	$87.88	7.333%	$94.3242	$94.32	$94.30	$94.30
Purchase #6	$133.61	4.269%	$139.3138	$139.31	$139.30	$139.30
Purchase #7	$35.35	6.511%	$37.6516	$37.65	$37.65	$37.70
7 purchase totals =	$1,026.27		$1,113.4620	$1,113.46	$1,113.45	$1,113.40