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	$54.94	4.683%	$57.5128	$57.51	$57.50	$57.50
Purchase #2	$37.31	6.818%	$39.8538	$39.85	$39.85	$39.90
Purchase #3	$20.40	9.407%	$22.319	$22.32	$22.30	$22.30
Purchase #4	$11.32	5.677%	$11.9626	$11.96	$11.95	$12.00
Purchase #5	$57.66	8.264%	$62.425	$62.43	$62.45	$62.40
Purchase #6	$90.59	7.696%	$97.5618	$97.56	$97.55	$97.60
Purchase #7	$188.25	11.725%	$210.3223	$210.32	$210.30	$210.30
7 purchase totals =	$460.47		$501.9573	$501.95	$501.90	$502.00