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	$31.54	6.726%	$33.6614	$33.66	$33.65	$33.70
Purchase #2	$171.45	13.665%	$194.8786	$194.88	$194.90	$194.90
Purchase #3	$44.45	8.261%	$48.122	$48.12	$48.10	$48.10
Purchase #4	$153.63	11.354%	$171.0732	$171.07	$171.05	$171.10
Purchase #5	$95.89	10.174%	$105.6458	$105.65	$105.65	$105.60
Purchase #6	$173.81	8.544%	$188.6603	$188.66	$188.65	$188.70
Purchase #7	$246.32	7.606%	$265.0551	$265.06	$265.05	$265.10
7 purchase totals =	$917.09		$1,007.0964	$1,007.10	$1,007.05	$1,007.20