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 $191.98   6.759%   $204.9559   $204.96   $204.95   $205.00  
  Purchase #2 $245.51   7.215%   $263.2235   $263.22   $263.20   $263.20  
  Purchase #3 $75.75   6.402%   $80.5995   $80.60   $80.60   $80.60  
  Purchase #4 $211.56   12.127%   $237.2159   $237.22   $237.20   $237.20  
  Purchase #5 $87.90   6.439%   $93.5599   $93.56   $93.55   $93.60  
  Purchase #6 $76.80   5.822%   $81.2713   $81.27   $81.25   $81.30  
  Purchase #7 $146.80   8.236%   $158.8904   $158.89   $158.90   $158.90  
  7 purchase totals = $1,036.30       $1,119.7164   $1,119.72   $1,119.65   $1,119.80