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	$183.81	4.174%	$191.4822	$191.48	$191.50	$191.50
Purchase #2	$78.99	12.664%	$88.9933	$88.99	$89.00	$89.00
Purchase #3	$80.84	12.488%	$90.9353	$90.94	$90.95	$90.90
Purchase #4	$9.69	11.725%	$10.8262	$10.83	$10.85	$10.80
Purchase #5	$114.54	11.310%	$127.4945	$127.49	$127.50	$127.50
Purchase #6	$243.26	5.566%	$256.7999	$256.80	$256.80	$256.80
Purchase #7	$235.94	12.484%	$265.3947	$265.39	$265.40	$265.40
7 purchase totals =	$947.07		$1,031.9261	$1,031.92	$1,032.00	$1,031.90