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	$7.29	9.229%	$7.9628	$7.96	$7.95	$8.00
Purchase #2	$81.35	10.154%	$89.6103	$89.61	$89.60	$89.60
Purchase #3	$23.43	13.526%	$26.5991	$26.60	$26.60	$26.60
Purchase #4	$176.50	8.835%	$192.0938	$192.09	$192.10	$192.10
Purchase #5	$85.57	8.331%	$92.6988	$92.70	$92.70	$92.70
Purchase #6	$183.91	3.595%	$190.5216	$190.52	$190.50	$190.50
Purchase #7	$89.38	5.172%	$94.0027	$94.00	$94.00	$94.00
7 purchase totals =	$647.43		$693.4891	$693.48	$693.45	$693.50