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	$168.75	10.842%	$187.0459	$187.05	$187.05	$187.00
Purchase #2	$113.67	8.629%	$123.4786	$123.48	$123.50	$123.50
Purchase #3	$79.34	3.719%	$82.2907	$82.29	$82.30	$82.30
Purchase #4	$167.59	13.259%	$189.8108	$189.81	$189.80	$189.80
Purchase #5	$125.35	9.485%	$137.2394	$137.24	$137.25	$137.20
Purchase #6	$69.48	12.274%	$78.008	$78.01	$78.00	$78.00
Purchase #7	$136.30	4.667%	$142.6611	$142.66	$142.65	$142.70
7 purchase totals =	$860.48		$940.5345	$940.54	$940.55	$940.50