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	$199.36	13.248%	$225.7712	$225.77	$225.75	$225.80
Purchase #2	$181.31	3.257%	$187.2153	$187.22	$187.20	$187.20
Purchase #3	$112.38	10.410%	$124.0788	$124.08	$124.10	$124.10
Purchase #4	$131.45	4.849%	$137.824	$137.82	$137.80	$137.80
Purchase #5	$85.39	11.835%	$95.4959	$95.50	$95.50	$95.50
Purchase #6	$53.73	7.736%	$57.8866	$57.89	$57.90	$57.90
Purchase #7	$164.90	6.792%	$176.1	$176.10	$176.10	$176.10
7 purchase totals =	$928.52		$1,004.3718	$1,004.38	$1,004.35	$1,004.40