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	$208.54	8.455%	$226.1721	$226.17	$226.15	$226.20
Purchase #2	$40.78	12.677%	$45.9497	$45.95	$45.95	$45.90
Purchase #3	$29.97	6.505%	$31.9195	$31.92	$31.90	$31.90
Purchase #4	$197.70	5.444%	$208.4628	$208.46	$208.45	$208.50
Purchase #5	$225.54	3.334%	$233.0595	$233.06	$233.05	$233.10
Purchase #6	$133.43	4.421%	$139.3289	$139.33	$139.35	$139.30
Purchase #7	$160.75	6.608%	$171.3724	$171.37	$171.35	$171.40
7 purchase totals =	$996.71		$1,056.2649	$1,056.26	$1,056.20	$1,056.30