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 $161.79   8.471%   $175.4952   $175.50   $175.50   $175.50  
  Purchase #2 $236.89   12.175%   $265.7314   $265.73   $265.75   $265.70  
  Purchase #3 $43.47   8.676%   $47.2415   $47.24   $47.25   $47.20  
  Purchase #4 $97.68   4.649%   $102.2211   $102.22   $102.20   $102.20  
  Purchase #5 $154.68   11.704%   $172.7837   $172.78   $172.80   $172.80  
  Purchase #6 $126.35   6.339%   $134.3593   $134.36   $134.35   $134.40  
  Purchase #7 $193.92   5.614%   $204.8067   $204.81   $204.80   $204.80  
  7 purchase totals = $1,014.78       $1,102.6389   $1,102.64   $1,102.65   $1,102.60