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	$62.38	7.108%	$66.814	$66.81	$66.80	$66.80
Purchase #2	$6.68	13.501%	$7.5819	$7.58	$7.60	$7.60
Purchase #3	$196.94	9.569%	$215.7852	$215.79	$215.80	$215.80
Purchase #4	$39.95	7.767%	$43.0529	$43.05	$43.05	$43.10
Purchase #5	$158.50	9.234%	$173.1359	$173.14	$173.15	$173.10
Purchase #6	$59.32	11.785%	$66.3109	$66.31	$66.30	$66.30
Purchase #7	$187.67	11.159%	$208.6121	$208.61	$208.60	$208.60
7 purchase totals =	$711.44		$781.2929	$781.29	$781.30	$781.30