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	$76.89	11.191%	$85.4948	$85.49	$85.50	$85.50
Purchase #2	$176.32	11.560%	$196.7026	$196.70	$196.70	$196.70
Purchase #3	$14.60	3.104%	$15.0532	$15.05	$15.05	$15.10
Purchase #4	$41.89	3.517%	$43.3633	$43.36	$43.35	$43.40
Purchase #5	$90.99	3.748%	$94.4003	$94.40	$94.40	$94.40
Purchase #6	$200.67	3.548%	$207.7898	$207.79	$207.80	$207.80
Purchase #7	$47.88	12.560%	$53.8937	$53.89	$53.90	$53.90
7 purchase totals =	$649.24		$696.6977	$696.68	$696.70	$696.80