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	$78.83	8.871%	$85.823	$85.82	$85.80	$85.80
Purchase #2	$83.42	8.181%	$90.2446	$90.24	$90.25	$90.20
Purchase #3	$38.60	6.733%	$41.1989	$41.20	$41.20	$41.20
Purchase #4	$246.86	9.757%	$270.9461	$270.95	$270.95	$270.90
Purchase #5	$227.61	5.582%	$240.3152	$240.32	$240.30	$240.30
Purchase #6	$128.28	4.344%	$133.8525	$133.85	$133.85	$133.90
Purchase #7	$66.77	8.670%	$72.559	$72.56	$72.55	$72.60
7 purchase totals =	$870.37		$934.9393	$934.94	$934.90	$934.90