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	$218.43	3.680%	$226.4682	$226.47	$226.45	$226.50
Purchase #2	$243.99	9.433%	$267.0056	$267.01	$267.00	$267.00
Purchase #3	$138.71	10.195%	$152.8515	$152.85	$152.85	$152.90
Purchase #4	$21.95	9.582%	$24.0532	$24.05	$24.05	$24.10
Purchase #5	$104.71	4.307%	$109.2199	$109.22	$109.20	$109.20
Purchase #6	$123.30	10.200%	$135.8766	$135.88	$135.90	$135.90
Purchase #7	$190.34	3.268%	$196.5603	$196.56	$196.55	$196.60
7 purchase totals =	$1,041.43		$1,112.0353	$1,112.04	$1,112.00	$1,112.20