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	$54.90	13.184%	$62.138	$62.14	$62.15	$62.10
Purchase #2	$240.49	7.345%	$258.154	$258.15	$258.15	$258.20
Purchase #3	$16.61	13.540%	$18.859	$18.86	$18.85	$18.90
Purchase #4	$222.89	6.793%	$238.0309	$238.03	$238.05	$238.00
Purchase #5	$200.73	7.401%	$215.586	$215.59	$215.60	$215.60
Purchase #6	$68.53	3.634%	$71.0204	$71.02	$71.00	$71.00
Purchase #7	$131.70	7.724%	$141.8725	$141.87	$141.85	$141.90
7 purchase totals =	$935.85		$1,005.6608	$1,005.66	$1,005.65	$1,005.70