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	$102.72	13.829%	$116.9251	$116.93	$116.95	$116.90
Purchase #2	$59.39	13.605%	$67.47	$67.47	$67.45	$67.50
Purchase #3	$200.98	10.219%	$221.5181	$221.52	$221.50	$221.50
Purchase #4	$198.42	8.518%	$215.3214	$215.32	$215.30	$215.30
Purchase #5	$34.42	3.767%	$35.7166	$35.72	$35.70	$35.70
Purchase #6	$56.47	12.156%	$63.3345	$63.33	$63.35	$63.30
Purchase #7	$187.29	11.183%	$208.2346	$208.23	$208.25	$208.20
7 purchase totals =	$839.69		$928.5203	$928.52	$928.50	$928.40