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	$183.90	6.691%	$196.2047	$196.20	$196.20	$196.20
Purchase #2	$136.54	6.372%	$145.2403	$145.24	$145.25	$145.20
Purchase #3	$44.89	9.715%	$49.2511	$49.25	$49.25	$49.30
Purchase #4	$120.45	10.505%	$133.1033	$133.10	$133.10	$133.10
Purchase #5	$209.38	6.423%	$222.8285	$222.83	$222.85	$222.80
Purchase #6	$246.55	7.271%	$264.4767	$264.48	$264.50	$264.50
Purchase #7	$19.34	8.147%	$20.9156	$20.92	$20.90	$20.90
7 purchase totals =	$961.05		$1,032.0202	$1,032.02	$1,032.05	$1,032.00