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 $59.87   4.641%   $62.6486   $62.65   $62.65   $62.60  
  Purchase #2 $24.45   6.238%   $25.9752   $25.98   $26.00   $26.00  
  Purchase #3 $158.43   13.562%   $179.9163   $179.92   $179.90   $179.90  
  Purchase #4 $55.33   12.171%   $62.0642   $62.06   $62.05   $62.10  
  Purchase #5 $6.25   6.179%   $6.6362   $6.64   $6.65   $6.60  
  Purchase #6 $9.77   10.550%   $10.8007   $10.80   $10.80   $10.80  
  Purchase #7 $111.39   11.290%   $123.9659   $123.97   $123.95   $124.00  
  7 purchase totals = $425.49       $472.0071   $472.02   $472.00   $472.00