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	$153.89	9.398%	$168.3526	$168.35	$168.35	$168.40
Purchase #2	$218.27	6.728%	$232.9552	$232.96	$232.95	$233.00
Purchase #3	$163.90	5.119%	$172.29	$172.29	$172.30	$172.30
Purchase #4	$164.25	9.530%	$179.903	$179.90	$179.90	$179.90
Purchase #5	$81.76	3.410%	$84.548	$84.55	$84.55	$84.50
Purchase #6	$37.90	13.853%	$43.1503	$43.15	$43.15	$43.20
Purchase #7	$14.81	7.205%	$15.8771	$15.88	$15.90	$15.90
7 purchase totals =	$834.78		$897.0762	$897.08	$897.10	$897.20