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 $184.64   11.387%   $205.665   $205.67   $205.65   $205.70  
  Purchase #2 $232.61   4.419%   $242.889   $242.89   $242.90   $242.90  
  Purchase #3 $190.87   12.536%   $214.7975   $214.80   $214.80   $214.80  
  Purchase #4 $244.52   8.652%   $265.6759   $265.68   $265.70   $265.70  
  Purchase #5 $189.49   7.104%   $202.9514   $202.95   $202.95   $203.00  
  Purchase #6 $192.41   5.663%   $203.3062   $203.31   $203.30   $203.30  
  Purchase #7 $148.81   8.205%   $161.0199   $161.02   $161.00   $161.00  
  7 purchase totals = $1,383.35       $1,496.3049   $1,496.32   $1,496.30   $1,496.40