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	$63.30	8.833%	$68.8913	$68.89	$68.90	$68.90
Purchase #2	$216.46	8.413%	$234.6708	$234.67	$234.65	$234.70
Purchase #3	$231.32	4.454%	$241.623	$241.62	$241.60	$241.60
Purchase #4	$224.86	7.334%	$241.3512	$241.35	$241.35	$241.40
Purchase #5	$231.99	10.746%	$256.9196	$256.92	$256.90	$256.90
Purchase #6	$82.30	6.208%	$87.4092	$87.41	$87.40	$87.40
Purchase #7	$85.51	7.393%	$91.8318	$91.83	$91.85	$91.80
7 purchase totals =	$1,135.74		$1,222.6969	$1,222.69	$1,222.65	$1,222.70