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	$12.88	12.205%	$14.452	$14.45	$14.45	$14.50
Purchase #2	$111.98	10.263%	$123.4725	$123.47	$123.45	$123.50
Purchase #3	$35.85	8.679%	$38.9614	$38.96	$38.95	$39.00
Purchase #4	$241.56	7.191%	$258.9306	$258.93	$258.95	$258.90
Purchase #5	$184.69	8.523%	$200.4311	$200.43	$200.45	$200.40
Purchase #6	$87.61	10.696%	$96.9808	$96.98	$97.00	$97.00
Purchase #7	$25.28	11.851%	$28.2759	$28.28	$28.30	$28.30
7 purchase totals =	$699.85		$761.5043	$761.50	$761.55	$761.60