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	$72.82	12.402%	$81.8511	$81.85	$81.85	$81.90
Purchase #2	$20.83	5.408%	$21.9565	$21.96	$21.95	$22.00
Purchase #3	$132.25	7.287%	$141.8871	$141.89	$141.90	$141.90
Purchase #4	$237.69	8.497%	$257.8865	$257.89	$257.90	$257.90
Purchase #5	$244.36	13.156%	$276.508	$276.51	$276.50	$276.50
Purchase #6	$96.55	12.745%	$108.8553	$108.86	$108.85	$108.90
Purchase #7	$118.66	6.328%	$126.1688	$126.17	$126.15	$126.20
7 purchase totals =	$923.16		$1,015.1133	$1,015.13	$1,015.10	$1,015.30