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	$223.58	13.468%	$253.6918	$253.69	$253.70	$253.70
Purchase #2	$11.80	13.418%	$13.3833	$13.38	$13.40	$13.40
Purchase #3	$40.77	6.411%	$43.3838	$43.38	$43.40	$43.40
Purchase #4	$141.58	10.807%	$156.8806	$156.88	$156.90	$156.90
Purchase #5	$196.62	5.836%	$208.0947	$208.09	$208.10	$208.10
Purchase #6	$13.56	13.227%	$15.3536	$15.35	$15.35	$15.40
Purchase #7	$166.66	4.367%	$173.938	$173.94	$173.95	$173.90
7 purchase totals =	$794.57		$864.7258	$864.71	$864.80	$864.80