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	$122.99	6.546%	$131.0409	$131.04	$131.05	$131.00
Purchase #2	$84.57	5.821%	$89.4928	$89.49	$89.50	$89.50
Purchase #3	$165.58	13.175%	$187.3952	$187.40	$187.40	$187.40
Purchase #4	$212.59	4.602%	$222.3734	$222.37	$222.35	$222.40
Purchase #5	$226.73	6.660%	$241.8302	$241.83	$241.85	$241.80
Purchase #6	$132.69	3.589%	$137.4522	$137.45	$137.45	$137.50
Purchase #7	$8.44	13.614%	$9.589	$9.59	$9.60	$9.60
7 purchase totals =	$953.59		$1,019.1737	$1,019.17	$1,019.20	$1,019.20