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 $117.41   6.652%   $125.2201   $125.22   $125.20   $125.20  
  Purchase #2 $177.75   5.709%   $187.8977   $187.90   $187.90   $187.90  
  Purchase #3 $155.35   6.221%   $165.0143   $165.01   $165.00   $165.00  
  Purchase #4 $23.77   9.133%   $25.9409   $25.94   $25.95   $25.90  
  Purchase #5 $150.36   6.772%   $160.5424   $160.54   $160.55   $160.50  
  Purchase #6 $211.69   7.338%   $227.2238   $227.22   $227.20   $227.20  
  Purchase #7 $131.72   9.563%   $144.3164   $144.32   $144.30   $144.30  
  7 purchase totals = $968.05       $1,036.1556   $1,036.15   $1,036.10   $1,036.00