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	$117.69	12.630%	$132.5542	$132.55	$132.55	$132.60
Purchase #2	$93.50	12.362%	$105.0585	$105.06	$105.05	$105.10
Purchase #3	$79.32	9.217%	$86.6309	$86.63	$86.65	$86.60
Purchase #4	$93.48	7.276%	$100.2816	$100.28	$100.30	$100.30
Purchase #5	$56.46	6.160%	$59.9379	$59.94	$59.95	$59.90
Purchase #6	$38.89	13.589%	$44.1748	$44.17	$44.15	$44.20
Purchase #7	$138.48	4.161%	$144.2422	$144.24	$144.25	$144.20
7 purchase totals =	$617.82		$672.8801	$672.87	$672.90	$672.90