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	$113.81	10.163%	$125.3765	$125.38	$125.40	$125.40
Purchase #2	$187.50	11.121%	$208.3519	$208.35	$208.35	$208.40
Purchase #3	$156.63	7.314%	$168.0859	$168.09	$168.10	$168.10
Purchase #4	$12.64	5.473%	$13.3318	$13.33	$13.35	$13.30
Purchase #5	$169.49	12.420%	$190.5407	$190.54	$190.55	$190.50
Purchase #6	$166.85	9.314%	$182.3904	$182.39	$182.40	$182.40
Purchase #7	$84.89	6.693%	$90.5717	$90.57	$90.55	$90.60
7 purchase totals =	$891.81		$978.6489	$978.65	$978.70	$978.70