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	$78.44	9.161%	$85.6259	$85.63	$85.65	$85.60
Purchase #2	$142.43	9.162%	$155.4794	$155.48	$155.50	$155.50
Purchase #3	$124.31	10.479%	$137.3364	$137.34	$137.35	$137.30
Purchase #4	$162.72	13.728%	$185.0582	$185.06	$185.05	$185.10
Purchase #5	$29.94	5.413%	$31.5607	$31.56	$31.55	$31.60
Purchase #6	$119.48	3.694%	$123.8936	$123.89	$123.90	$123.90
Purchase #7	$80.84	7.580%	$86.9677	$86.97	$86.95	$87.00
7 purchase totals =	$738.16		$805.9219	$805.93	$805.95	$806.00