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	$110.53	9.162%	$120.6568	$120.66	$120.65	$120.70
Purchase #2	$69.34	6.715%	$73.9962	$74.00	$74.00	$74.00
Purchase #3	$56.57	9.110%	$61.7235	$61.72	$61.70	$61.70
Purchase #4	$14.82	3.698%	$15.368	$15.37	$15.35	$15.40
Purchase #5	$72.66	4.629%	$76.0234	$76.02	$76.00	$76.00
Purchase #6	$101.96	9.631%	$111.7798	$111.78	$111.80	$111.80
Purchase #7	$105.37	5.845%	$111.5289	$111.53	$111.55	$111.50
7 purchase totals =	$531.25		$571.0766	$571.08	$571.05	$571.10