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	$213.95	11.208%	$237.9295	$237.93	$237.95	$237.90
Purchase #2	$83.92	6.744%	$89.5796	$89.58	$89.60	$89.60
Purchase #3	$244.71	8.479%	$265.459	$265.46	$265.45	$265.50
Purchase #4	$40.50	10.418%	$44.7193	$44.72	$44.70	$44.70
Purchase #5	$201.31	8.807%	$219.0394	$219.04	$219.05	$219.00
Purchase #6	$33.37	6.611%	$35.5761	$35.58	$35.60	$35.60
Purchase #7	$35.64	12.446%	$40.0758	$40.08	$40.10	$40.10
7 purchase totals =	$853.40		$932.3787	$932.39	$932.45	$932.40