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	$157.63	4.558%	$164.8148	$164.81	$164.80	$164.80
Purchase #2	$87.32	4.859%	$91.5629	$91.56	$91.55	$91.60
Purchase #3	$11.81	6.858%	$12.6199	$12.62	$12.60	$12.60
Purchase #4	$89.50	12.294%	$100.5031	$100.50	$100.50	$100.50
Purchase #5	$41.38	11.199%	$46.0141	$46.01	$46.00	$46.00
Purchase #6	$186.52	9.288%	$203.844	$203.84	$203.85	$203.80
Purchase #7	$201.32	11.725%	$224.9248	$224.92	$224.90	$224.90
7 purchase totals =	$775.48		$844.2836	$844.26	$844.20	$844.20