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	$41.25	7.410%	$44.3066	$44.31	$44.30	$44.30
Purchase #2	$242.40	12.145%	$271.8395	$271.84	$271.85	$271.80
Purchase #3	$239.70	5.763%	$253.5139	$253.51	$253.50	$253.50
Purchase #4	$136.93	3.744%	$142.0567	$142.06	$142.05	$142.10
Purchase #5	$151.86	8.319%	$164.4932	$164.49	$164.50	$164.50
Purchase #6	$40.43	11.353%	$45.02	$45.02	$45.00	$45.00
Purchase #7	$180.33	6.248%	$191.597	$191.60	$191.60	$191.60
7 purchase totals =	$1,032.90		$1,112.8269	$1,112.83	$1,112.80	$1,112.80