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	$200.92	8.797%	$218.5949	$218.59	$218.60	$218.60
Purchase #2	$64.50	10.791%	$71.4602	$71.46	$71.45	$71.50
Purchase #3	$44.44	4.864%	$46.6016	$46.60	$46.60	$46.60
Purchase #4	$130.81	8.207%	$141.5456	$141.55	$141.55	$141.50
Purchase #5	$59.67	11.115%	$66.3023	$66.30	$66.30	$66.30
Purchase #6	$242.38	5.440%	$255.5655	$255.57	$255.55	$255.60
Purchase #7	$98.83	7.276%	$106.0209	$106.02	$106.00	$106.00
7 purchase totals =	$841.55		$906.0910	$906.09	$906.05	$906.10