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	$87.80	10.277%	$96.8232	$96.82	$96.80	$96.80
Purchase #2	$211.80	7.182%	$227.0115	$227.01	$227.00	$227.00
Purchase #3	$14.69	6.788%	$15.6872	$15.69	$15.70	$15.70
Purchase #4	$82.70	7.416%	$88.833	$88.83	$88.85	$88.80
Purchase #5	$52.89	12.552%	$59.5288	$59.53	$59.55	$59.50
Purchase #6	$34.35	10.740%	$38.0392	$38.04	$38.05	$38.00
Purchase #7	$103.31	8.247%	$111.83	$111.83	$111.85	$111.80
7 purchase totals =	$587.54		$637.7529	$637.75	$637.80	$637.60