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 $187.93   7.600%   $202.2127   $202.21   $202.20   $202.20  
  Purchase #2 $137.43   12.592%   $154.7352   $154.74   $154.75   $154.70  
  Purchase #3 $43.47   11.542%   $48.4873   $48.49   $48.50   $48.50  
  Purchase #4 $228.34   13.225%   $258.538   $258.54   $258.55   $258.50  
  Purchase #5 $93.90   4.281%   $97.9199   $97.92   $97.90   $97.90  
  Purchase #6 $154.49   8.229%   $167.203   $167.20   $167.20   $167.20  
  Purchase #7 $180.87   8.118%   $195.553   $195.55   $195.55   $195.60  
  7 purchase totals = $1,026.43       $1,124.6491   $1,124.65   $1,124.65   $1,124.60