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	$137.83	6.350%	$146.5822	$146.58	$146.60	$146.60
Purchase #2	$49.29	4.387%	$51.4524	$51.45	$51.45	$51.50
Purchase #3	$225.26	8.136%	$243.5872	$243.59	$243.60	$243.60
Purchase #4	$179.27	10.179%	$197.5179	$197.52	$197.50	$197.50
Purchase #5	$178.74	11.874%	$199.9636	$199.96	$199.95	$200.00
Purchase #6	$87.57	3.426%	$90.5701	$90.57	$90.55	$90.60
Purchase #7	$138.83	4.409%	$144.951	$144.95	$144.95	$145.00
7 purchase totals =	$996.79		$1,074.6244	$1,074.62	$1,074.60	$1,074.80