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	$213.81	4.136%	$222.6532	$222.65	$222.65	$222.70
Purchase #2	$138.42	3.215%	$142.8702	$142.87	$142.85	$142.90
Purchase #3	$80.96	8.169%	$87.5736	$87.57	$87.55	$87.60
Purchase #4	$41.52	9.267%	$45.3677	$45.37	$45.35	$45.40
Purchase #5	$61.41	11.201%	$68.2885	$68.29	$68.30	$68.30
Purchase #6	$119.72	3.540%	$123.9581	$123.96	$123.95	$124.00
Purchase #7	$196.90	13.692%	$223.8595	$223.86	$223.85	$223.90
7 purchase totals =	$852.74		$914.5708	$914.57	$914.50	$914.80