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	$34.58	3.688%	$35.8553	$35.86	$35.85	$35.90
Purchase #2	$65.45	6.568%	$69.7488	$69.75	$69.75	$69.70
Purchase #3	$69.68	12.387%	$78.3113	$78.31	$78.30	$78.30
Purchase #4	$39.85	5.427%	$42.0127	$42.01	$42.00	$42.00
Purchase #5	$223.59	8.835%	$243.3442	$243.34	$243.35	$243.30
Purchase #6	$232.55	8.169%	$251.547	$251.55	$251.55	$251.50
Purchase #7	$245.93	10.103%	$270.7763	$270.78	$270.80	$270.80
7 purchase totals =	$911.63		$991.5956	$991.60	$991.60	$991.50