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	$59.79	12.342%	$67.1693	$67.17	$67.15	$67.20
Purchase #2	$13.94	6.146%	$14.7968	$14.80	$14.80	$14.80
Purchase #3	$230.71	13.642%	$262.1835	$262.18	$262.20	$262.20
Purchase #4	$96.90	8.536%	$105.1714	$105.17	$105.15	$105.20
Purchase #5	$216.58	8.122%	$234.1706	$234.17	$234.15	$234.20
Purchase #6	$172.29	13.840%	$196.1349	$196.13	$196.15	$196.10
Purchase #7	$173.55	7.328%	$186.2677	$186.27	$186.25	$186.30
7 purchase totals =	$963.76		$1,065.8942	$1,065.89	$1,065.85	$1,066.00