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	$221.51	5.353%	$233.3674	$233.37	$233.35	$233.40
Purchase #2	$214.57	11.579%	$239.4151	$239.42	$239.40	$239.40
Purchase #3	$43.96	3.188%	$45.3614	$45.36	$45.35	$45.40
Purchase #4	$71.67	9.529%	$78.4994	$78.50	$78.50	$78.50
Purchase #5	$161.37	3.476%	$166.9792	$166.98	$167.00	$167.00
Purchase #6	$93.39	6.352%	$99.3221	$99.32	$99.30	$99.30
Purchase #7	$35.96	5.537%	$37.9511	$37.95	$37.95	$38.00
7 purchase totals =	$842.43		$900.8957	$900.90	$900.85	$901.00