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	$146.96	6.113%	$155.9437	$155.94	$155.95	$155.90
Purchase #2	$167.91	11.358%	$186.9812	$186.98	$187.00	$187.00
Purchase #3	$185.82	3.833%	$192.9425	$192.94	$192.95	$192.90
Purchase #4	$34.37	4.537%	$35.9294	$35.93	$35.95	$35.90
Purchase #5	$96.71	12.788%	$109.0773	$109.08	$109.10	$109.10
Purchase #6	$111.83	5.366%	$117.8308	$117.83	$117.85	$117.80
Purchase #7	$242.28	3.526%	$250.8228	$250.82	$250.80	$250.80
7 purchase totals =	$985.88		$1,049.5277	$1,049.52	$1,049.60	$1,049.40