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	$78.49	10.688%	$86.879	$86.88	$86.90	$86.90
Purchase #2	$37.85	5.388%	$39.8894	$39.89	$39.90	$39.90
Purchase #3	$100.37	12.424%	$112.84	$112.84	$112.85	$112.80
Purchase #4	$88.67	10.362%	$97.858	$97.86	$97.85	$97.90
Purchase #5	$83.67	13.754%	$95.178	$95.18	$95.20	$95.20
Purchase #6	$226.90	12.775%	$255.8865	$255.89	$255.90	$255.90
Purchase #7	$240.66	11.403%	$268.1025	$268.10	$268.10	$268.10
7 purchase totals =	$856.61		$956.6334	$956.64	$956.70	$956.70