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 $216.52   7.268%   $232.2567   $232.26   $232.25   $232.30  
  Purchase #2 $239.97   12.387%   $269.6951   $269.70   $269.70   $269.70  
  Purchase #3 $238.47   8.105%   $257.798   $257.80   $257.80   $257.80  
  Purchase #4 $103.29   11.379%   $115.0434   $115.04   $115.05   $115.00  
  Purchase #5 $125.94   9.583%   $138.0088   $138.01   $138.00   $138.00  
  Purchase #6 $172.47   9.732%   $189.2548   $189.25   $189.25   $189.30  
  Purchase #7 $111.84   11.569%   $124.7788   $124.78   $124.80   $124.80  
  7 purchase totals = $1,208.50       $1,326.8356   $1,326.84   $1,326.85   $1,326.90