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 $108.61   7.439%   $116.6895   $116.69   $116.70   $116.70  
  Purchase #2 $49.82   4.713%   $52.168   $52.17   $52.15   $52.20  
  Purchase #3 $45.52   13.317%   $51.5819   $51.58   $51.60   $51.60  
  Purchase #4 $88.67   11.299%   $98.6888   $98.69   $98.70   $98.70  
  Purchase #5 $196.99   13.746%   $224.0682   $224.07   $224.05   $224.10  
  Purchase #6 $245.45   4.786%   $257.1972   $257.20   $257.20   $257.20  
  Purchase #7 $48.61   7.671%   $52.3389   $52.34   $52.35   $52.30  
  7 purchase totals = $783.67       $852.7325   $852.74   $852.75   $852.80