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	$98.48	13.375%	$111.6517	$111.65	$111.65	$111.70
Purchase #2	$170.93	4.681%	$178.9312	$178.93	$178.95	$178.90
Purchase #3	$150.59	3.655%	$156.0941	$156.09	$156.10	$156.10
Purchase #4	$162.37	6.514%	$172.9468	$172.95	$172.95	$172.90
Purchase #5	$19.93	8.747%	$21.6733	$21.67	$21.65	$21.70
Purchase #6	$134.53	6.432%	$143.183	$143.18	$143.20	$143.20
Purchase #7	$50.41	6.693%	$53.7839	$53.78	$53.80	$53.80
7 purchase totals =	$787.24		$838.2640	$838.25	$838.30	$838.30