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	$241.79	13.532%	$274.509	$274.51	$274.50	$274.50
Purchase #2	$79.32	3.236%	$81.8868	$81.89	$81.90	$81.90
Purchase #3	$44.73	6.789%	$47.7667	$47.77	$47.75	$47.80
Purchase #4	$90.42	11.109%	$100.4648	$100.46	$100.45	$100.50
Purchase #5	$196.82	5.850%	$208.334	$208.33	$208.35	$208.30
Purchase #6	$239.90	12.627%	$270.1922	$270.19	$270.20	$270.20
Purchase #7	$62.45	10.313%	$68.8905	$68.89	$68.90	$68.90
7 purchase totals =	$955.43		$1,052.0440	$1,052.04	$1,052.05	$1,052.10