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	$198.47	4.742%	$207.8814	$207.88	$207.90	$207.90
Purchase #2	$93.85	12.124%	$105.2284	$105.23	$105.25	$105.20
Purchase #3	$94.67	5.545%	$99.9195	$99.92	$99.90	$99.90
Purchase #4	$88.64	9.544%	$97.0998	$97.10	$97.10	$97.10
Purchase #5	$238.88	10.762%	$264.5883	$264.59	$264.60	$264.60
Purchase #6	$145.89	4.584%	$152.5776	$152.58	$152.60	$152.60
Purchase #7	$35.97	7.185%	$38.5544	$38.55	$38.55	$38.60
7 purchase totals =	$896.37		$965.8494	$965.85	$965.90	$965.90