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	$153.35	7.253%	$164.4725	$164.47	$164.45	$164.50
Purchase #2	$148.58	13.424%	$168.5254	$168.53	$168.55	$168.50
Purchase #3	$78.66	9.634%	$86.2381	$86.24	$86.25	$86.20
Purchase #4	$177.88	5.591%	$187.8253	$187.83	$187.85	$187.80
Purchase #5	$64.29	4.393%	$67.1143	$67.11	$67.10	$67.10
Purchase #6	$36.43	13.198%	$41.238	$41.24	$41.25	$41.20
Purchase #7	$231.45	6.698%	$246.9525	$246.95	$246.95	$247.00
7 purchase totals =	$890.64		$962.3661	$962.37	$962.40	$962.30