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	$68.95	3.347%	$71.2578	$71.26	$71.25	$71.30
Purchase #2	$229.71	12.408%	$258.2124	$258.21	$258.20	$258.20
Purchase #3	$72.59	10.796%	$80.4268	$80.43	$80.45	$80.40
Purchase #4	$239.79	9.318%	$262.1336	$262.13	$262.15	$262.10
Purchase #5	$118.89	12.621%	$133.8951	$133.90	$133.90	$133.90
Purchase #6	$223.61	10.491%	$247.0689	$247.07	$247.05	$247.10
Purchase #7	$69.93	11.643%	$78.0719	$78.07	$78.05	$78.10
7 purchase totals =	$1,023.47		$1,131.0665	$1,131.07	$1,131.05	$1,131.10