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	$189.31	13.763%	$215.3647	$215.36	$215.35	$215.40
Purchase #2	$68.29	11.286%	$75.9972	$76.00	$76.00	$76.00
Purchase #3	$177.54	9.611%	$194.6034	$194.60	$194.60	$194.60
Purchase #4	$100.43	8.426%	$108.8922	$108.89	$108.90	$108.90
Purchase #5	$246.31	10.221%	$271.4853	$271.49	$271.50	$271.50
Purchase #6	$85.64	8.113%	$92.588	$92.59	$92.60	$92.60
Purchase #7	$81.53	10.846%	$90.3727	$90.37	$90.35	$90.40
7 purchase totals =	$949.05		$1,049.3035	$1,049.30	$1,049.30	$1,049.40