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	$111.62	5.355%	$117.5973	$117.60	$117.60	$117.60
Purchase #2	$62.47	7.598%	$67.2165	$67.22	$67.20	$67.20
Purchase #3	$190.78	12.216%	$214.0857	$214.09	$214.10	$214.10
Purchase #4	$212.68	4.636%	$222.5398	$222.54	$222.55	$222.50
Purchase #5	$97.38	12.523%	$109.5749	$109.57	$109.55	$109.60
Purchase #6	$106.63	10.595%	$117.9274	$117.93	$117.95	$117.90
Purchase #7	$195.25	11.419%	$217.5456	$217.55	$217.55	$217.50
7 purchase totals =	$976.81		$1,066.4872	$1,066.50	$1,066.50	$1,066.40