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 $94.30   13.197%   $106.7448   $106.74   $106.75   $106.70  
  Purchase #2 $187.70   8.791%   $204.2007   $204.20   $204.20   $204.20  
  Purchase #3 $52.97   7.855%   $57.1308   $57.13   $57.15   $57.10  
  Purchase #4 $53.49   10.177%   $58.9337   $58.93   $58.95   $58.90  
  Purchase #5 $228.78   7.397%   $245.7029   $245.70   $245.70   $245.70  
  Purchase #6 $56.86   8.254%   $61.5532   $61.55   $61.55   $61.60  
  Purchase #7 $242.82   7.391%   $260.7668   $260.77   $260.75   $260.80  
  7 purchase totals = $916.92       $995.0329   $995.02   $995.05   $995.00