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	$11.52	10.558%	$12.7363	$12.74	$12.75	$12.70
Purchase #2	$86.94	12.277%	$97.6136	$97.61	$97.60	$97.60
Purchase #3	$98.59	13.563%	$111.9618	$111.96	$111.95	$112.00
Purchase #4	$179.93	11.455%	$200.541	$200.54	$200.55	$200.50
Purchase #5	$220.48	10.206%	$242.9822	$242.98	$243.00	$243.00
Purchase #6	$139.59	13.614%	$158.5938	$158.59	$158.60	$158.60
Purchase #7	$32.54	12.455%	$36.5929	$36.59	$36.60	$36.60
7 purchase totals =	$769.59		$861.0216	$861.01	$861.05	$861.00