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 $87.69   8.387%   $95.0446   $95.04   $95.05   $95.00  
  Purchase #2 $249.37   6.611%   $265.8559   $265.86   $265.85   $265.90  
  Purchase #3 $112.45   9.739%   $123.4015   $123.40   $123.40   $123.40  
  Purchase #4 $121.31   6.304%   $128.9574   $128.96   $128.95   $129.00  
  Purchase #5 $244.78   5.267%   $257.6726   $257.67   $257.65   $257.70  
  Purchase #6 $124.42   13.477%   $141.1881   $141.19   $141.20   $141.20  
  Purchase #7 $225.61   6.294%   $239.8099   $239.81   $239.80   $239.80  
  7 purchase totals = $1,165.63       $1,251.9300   $1,251.93   $1,251.90   $1,252.00