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	$241.74	8.748%	$262.8874	$262.89	$262.90	$262.90
Purchase #2	$232.30	13.130%	$262.801	$262.80	$262.80	$262.80
Purchase #3	$107.89	8.615%	$117.1847	$117.18	$117.20	$117.20
Purchase #4	$26.32	9.849%	$28.9123	$28.91	$28.90	$28.90
Purchase #5	$133.51	5.814%	$141.2723	$141.27	$141.25	$141.30
Purchase #6	$167.95	6.665%	$179.1439	$179.14	$179.15	$179.10
Purchase #7	$124.41	12.141%	$139.5146	$139.51	$139.50	$139.50
7 purchase totals =	$1,034.12		$1,131.7162	$1,131.70	$1,131.70	$1,131.70