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 $92.60   5.417%   $97.6161   $97.62   $97.60   $97.60  
  Purchase #2 $104.79   13.481%   $118.9167   $118.92   $118.90   $118.90  
  Purchase #3 $179.66   5.767%   $190.021   $190.02   $190.00   $190.00  
  Purchase #4 $57.59   8.719%   $62.6113   $62.61   $62.60   $62.60  
  Purchase #5 $133.49   12.582%   $150.2857   $150.29   $150.30   $150.30  
  Purchase #6 $105.81   4.871%   $110.964   $110.96   $110.95   $111.00  
  Purchase #7 $14.62   10.685%   $16.1821   $16.18   $16.20   $16.20  
  7 purchase totals = $688.56       $746.5969   $746.60   $746.55   $746.60