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	$199.43	10.638%	$220.6454	$220.65	$220.65	$220.60
Purchase #2	$9.58	11.829%	$10.7132	$10.71	$10.70	$10.70
Purchase #3	$132.96	3.228%	$137.2519	$137.25	$137.25	$137.30
Purchase #4	$206.27	10.795%	$228.5368	$228.54	$228.55	$228.50
Purchase #5	$95.73	4.847%	$100.37	$100.37	$100.35	$100.40
Purchase #6	$165.48	8.527%	$179.5905	$179.59	$179.60	$179.60
Purchase #7	$146.27	12.344%	$164.3256	$164.33	$164.35	$164.30
7 purchase totals =	$955.72		$1,041.4334	$1,041.44	$1,041.45	$1,041.40