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	$126.73	4.825%	$132.8447	$132.84	$132.85	$132.80
Purchase #2	$62.78	7.672%	$67.5965	$67.60	$67.60	$67.60
Purchase #3	$169.46	6.867%	$181.0968	$181.10	$181.10	$181.10
Purchase #4	$50.46	12.726%	$56.8815	$56.88	$56.90	$56.90
Purchase #5	$114.89	7.378%	$123.3666	$123.37	$123.35	$123.40
Purchase #6	$143.78	6.141%	$152.6095	$152.61	$152.60	$152.60
Purchase #7	$51.61	11.237%	$57.4094	$57.41	$57.40	$57.40
7 purchase totals =	$719.71		$771.8050	$771.81	$771.80	$771.80