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	$217.34	5.147%	$228.5265	$228.53	$228.55	$228.50
Purchase #2	$33.59	9.572%	$36.8052	$36.81	$36.80	$36.80
Purchase #3	$98.68	12.497%	$111.012	$111.01	$111.00	$111.00
Purchase #4	$105.26	6.454%	$112.0535	$112.05	$112.05	$112.10
Purchase #5	$123.33	11.548%	$137.5721	$137.57	$137.55	$137.60
Purchase #6	$153.31	11.804%	$171.4067	$171.41	$171.40	$171.40
Purchase #7	$135.83	7.480%	$145.9901	$145.99	$146.00	$146.00
7 purchase totals =	$867.34		$943.3661	$943.37	$943.35	$943.40