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	$63.39	12.740%	$71.4659	$71.47	$71.45	$71.50
Purchase #2	$76.78	13.680%	$87.2835	$87.28	$87.30	$87.30
Purchase #3	$183.40	5.580%	$193.6337	$193.63	$193.65	$193.60
Purchase #4	$75.99	3.209%	$78.4285	$78.43	$78.45	$78.40
Purchase #5	$100.41	4.680%	$105.1092	$105.11	$105.10	$105.10
Purchase #6	$24.28	3.296%	$25.0803	$25.08	$25.10	$25.10
Purchase #7	$144.89	5.739%	$153.2052	$153.21	$153.20	$153.20
7 purchase totals =	$669.14		$714.2063	$714.21	$714.25	$714.20