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	$126.95	4.204%	$132.287	$132.29	$132.30	$132.30
Purchase #2	$19.82	5.263%	$20.8631	$20.86	$20.85	$20.90
Purchase #3	$105.70	7.682%	$113.8199	$113.82	$113.80	$113.80
Purchase #4	$199.78	7.650%	$215.0632	$215.06	$215.05	$215.10
Purchase #5	$169.29	9.352%	$185.122	$185.12	$185.10	$185.10
Purchase #6	$64.83	6.277%	$68.8994	$68.90	$68.90	$68.90
Purchase #7	$109.37	3.705%	$113.4222	$113.42	$113.40	$113.40
7 purchase totals =	$795.74		$849.4768	$849.47	$849.40	$849.50