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	$69.52	10.714%	$76.9684	$76.97	$76.95	$77.00
Purchase #2	$56.94	13.354%	$64.5438	$64.54	$64.55	$64.50
Purchase #3	$83.25	10.600%	$92.0745	$92.07	$92.05	$92.10
Purchase #4	$131.30	9.374%	$143.6081	$143.61	$143.60	$143.60
Purchase #5	$74.43	12.465%	$83.7077	$83.71	$83.70	$83.70
Purchase #6	$6.51	4.683%	$6.8149	$6.81	$6.80	$6.80
Purchase #7	$19.36	6.350%	$20.5894	$20.59	$20.60	$20.60
7 purchase totals =	$441.31		$488.3068	$488.30	$488.25	$488.30