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	$64.58	6.191%	$68.5781	$68.58	$68.60	$68.60
Purchase #2	$215.81	3.708%	$223.8122	$223.81	$223.80	$223.80
Purchase #3	$75.97	13.722%	$86.3946	$86.39	$86.40	$86.40
Purchase #4	$143.57	9.269%	$156.8775	$156.88	$156.90	$156.90
Purchase #5	$82.60	4.786%	$86.5532	$86.55	$86.55	$86.60
Purchase #6	$40.95	6.311%	$43.5344	$43.53	$43.55	$43.50
Purchase #7	$37.30	6.855%	$39.8569	$39.86	$39.85	$39.90
7 purchase totals =	$660.78		$705.6069	$705.60	$705.65	$705.70