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 $59.48   5.643%   $62.8365   $62.84   $62.85   $62.80  
  Purchase #2 $225.46   11.211%   $250.7363   $250.74   $250.75   $250.70  
  Purchase #3 $15.85   11.382%   $17.654   $17.65   $17.65   $17.70  
  Purchase #4 $223.90   9.418%   $244.9869   $244.99   $245.00   $245.00  
  Purchase #5 $179.46   12.490%   $201.8746   $201.87   $201.85   $201.90  
  Purchase #6 $31.54   9.350%   $34.489   $34.49   $34.50   $34.50  
  Purchase #7 $170.76   6.635%   $182.0899   $182.09   $182.10   $182.10  
  7 purchase totals = $906.45       $994.6672   $994.67   $994.70   $994.70