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	$40.70	12.686%	$45.8632	$45.86	$45.85	$45.90
Purchase #2	$176.30	8.104%	$190.5874	$190.59	$190.60	$190.60
Purchase #3	$155.81	5.348%	$164.1427	$164.14	$164.15	$164.10
Purchase #4	$232.71	8.854%	$253.3141	$253.31	$253.30	$253.30
Purchase #5	$109.47	7.213%	$117.3661	$117.37	$117.35	$117.40
Purchase #6	$91.26	6.315%	$97.0231	$97.02	$97.00	$97.00
Purchase #7	$229.84	13.258%	$260.3122	$260.31	$260.30	$260.30
7 purchase totals =	$1,036.09		$1,128.6088	$1,128.60	$1,128.55	$1,128.60