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	$111.64	13.658%	$126.8878	$126.89	$126.90	$126.90
Purchase #2	$137.77	8.838%	$149.9461	$149.95	$149.95	$149.90
Purchase #3	$144.80	6.630%	$154.4002	$154.40	$154.40	$154.40
Purchase #4	$189.93	5.580%	$200.5281	$200.53	$200.55	$200.50
Purchase #5	$73.43	12.102%	$82.3165	$82.32	$82.30	$82.30
Purchase #6	$40.34	7.817%	$43.4934	$43.49	$43.50	$43.50
Purchase #7	$245.29	4.467%	$256.2471	$256.25	$256.25	$256.20
7 purchase totals =	$943.20		$1,013.8192	$1,013.83	$1,013.85	$1,013.70