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	$11.37	11.631%	$12.6924	$12.69	$12.70	$12.70
Purchase #2	$120.38	4.796%	$126.1534	$126.15	$126.15	$126.20
Purchase #3	$228.50	11.808%	$255.4813	$255.48	$255.50	$255.50
Purchase #4	$82.52	12.235%	$92.6163	$92.62	$92.60	$92.60
Purchase #5	$125.44	3.445%	$129.7614	$129.76	$129.75	$129.80
Purchase #6	$186.25	7.864%	$200.8967	$200.90	$200.90	$200.90
Purchase #7	$240.34	9.797%	$263.8861	$263.89	$263.90	$263.90
7 purchase totals =	$994.80		$1,081.4876	$1,081.49	$1,081.50	$1,081.60