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	$202.81	13.714%	$230.6234	$230.62	$230.60	$230.60
Purchase #2	$6.89	12.497%	$7.751	$7.75	$7.75	$7.80
Purchase #3	$98.90	12.372%	$111.1359	$111.14	$111.15	$111.10
Purchase #4	$140.71	3.388%	$145.4773	$145.48	$145.50	$145.50
Purchase #5	$229.38	10.656%	$253.8227	$253.82	$253.80	$253.80
Purchase #6	$132.53	10.660%	$146.6577	$146.66	$146.65	$146.70
Purchase #7	$168.52	13.321%	$190.9685	$190.97	$190.95	$191.00
7 purchase totals =	$979.74		$1,086.4365	$1,086.44	$1,086.40	$1,086.50