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	$93.34	9.801%	$102.4883	$102.49	$102.50	$102.50
Purchase #2	$49.96	3.156%	$51.5367	$51.54	$51.55	$51.50
Purchase #3	$243.32	11.192%	$270.5524	$270.55	$270.55	$270.60
Purchase #4	$13.78	5.746%	$14.5718	$14.57	$14.55	$14.60
Purchase #5	$198.67	9.228%	$217.0033	$217.00	$217.00	$217.00
Purchase #6	$131.61	7.540%	$141.5334	$141.53	$141.55	$141.50
Purchase #7	$130.85	9.717%	$143.5647	$143.56	$143.55	$143.60
7 purchase totals =	$861.53		$941.2506	$941.24	$941.25	$941.30