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	$83.81	10.227%	$92.3812	$92.38	$92.40	$92.40
Purchase #2	$135.53	4.698%	$141.8972	$141.90	$141.90	$141.90
Purchase #3	$79.95	7.370%	$85.8423	$85.84	$85.85	$85.80
Purchase #4	$233.87	10.523%	$258.4801	$258.48	$258.50	$258.50
Purchase #5	$213.84	6.338%	$227.3932	$227.39	$227.40	$227.40
Purchase #6	$89.92	11.262%	$100.0468	$100.05	$100.05	$100.00
Purchase #7	$63.59	9.319%	$69.516	$69.52	$69.50	$69.50
7 purchase totals =	$900.51		$975.5568	$975.56	$975.60	$975.50