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	$236.60	5.491%	$249.5917	$249.59	$249.60	$249.60
Purchase #2	$8.69	6.615%	$9.2648	$9.26	$9.25	$9.30
Purchase #3	$32.90	3.650%	$34.1009	$34.10	$34.10	$34.10
Purchase #4	$105.76	10.535%	$116.9018	$116.90	$116.90	$116.90
Purchase #5	$105.93	5.676%	$111.9426	$111.94	$111.95	$111.90
Purchase #6	$165.43	6.127%	$175.5659	$175.57	$175.55	$175.60
Purchase #7	$170.47	11.387%	$189.8814	$189.88	$189.90	$189.90
7 purchase totals =	$825.78		$887.2491	$887.24	$887.25	$887.30