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	$31.32	7.482%	$33.6634	$33.66	$33.65	$33.70
Purchase #2	$42.83	3.338%	$44.2597	$44.26	$44.25	$44.30
Purchase #3	$241.56	12.293%	$271.255	$271.26	$271.25	$271.30
Purchase #4	$226.99	7.444%	$243.8871	$243.89	$243.90	$243.90
Purchase #5	$240.95	6.211%	$255.9154	$255.92	$255.90	$255.90
Purchase #6	$67.31	7.791%	$72.5541	$72.55	$72.55	$72.60
Purchase #7	$10.87	5.370%	$11.4537	$11.45	$11.45	$11.50
7 purchase totals =	$861.83		$932.9884	$932.99	$932.95	$933.20