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	$67.42	9.475%	$73.808	$73.81	$73.80	$73.80
Purchase #2	$101.63	3.815%	$105.5072	$105.51	$105.50	$105.50
Purchase #3	$116.27	10.123%	$128.04	$128.04	$128.05	$128.00
Purchase #4	$141.74	3.296%	$146.4118	$146.41	$146.40	$146.40
Purchase #5	$164.85	7.258%	$176.8148	$176.81	$176.80	$176.80
Purchase #6	$187.76	5.678%	$198.421	$198.42	$198.40	$198.40
Purchase #7	$65.47	10.256%	$72.1846	$72.18	$72.20	$72.20
7 purchase totals =	$845.14		$901.1874	$901.18	$901.15	$901.10