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	$108.49	4.663%	$113.5489	$113.55	$113.55	$113.50
Purchase #2	$146.35	12.613%	$164.8091	$164.81	$164.80	$164.80
Purchase #3	$133.62	8.311%	$144.7252	$144.73	$144.75	$144.70
Purchase #4	$42.67	7.448%	$45.8481	$45.85	$45.85	$45.80
Purchase #5	$140.51	3.135%	$144.915	$144.92	$144.90	$144.90
Purchase #6	$131.39	10.678%	$145.4198	$145.42	$145.40	$145.40
Purchase #7	$170.60	12.167%	$191.3569	$191.36	$191.35	$191.40
7 purchase totals =	$873.63		$950.6230	$950.64	$950.60	$950.50