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	$82.38	12.270%	$92.488	$92.49	$92.50	$92.50
Purchase #2	$7.38	7.409%	$7.9268	$7.93	$7.95	$7.90
Purchase #3	$51.82	10.477%	$57.2492	$57.25	$57.25	$57.20
Purchase #4	$244.35	10.730%	$270.5688	$270.57	$270.55	$270.60
Purchase #5	$247.43	7.492%	$265.9675	$265.97	$265.95	$266.00
Purchase #6	$28.52	13.706%	$32.429	$32.43	$32.45	$32.40
Purchase #7	$12.48	7.319%	$13.3934	$13.39	$13.40	$13.40
7 purchase totals =	$674.36		$740.0227	$740.03	$740.05	$740.00