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 $114.76   7.342%   $123.1857   $123.19   $123.20   $123.20  
  Purchase #2 $223.34   10.235%   $246.1988   $246.20   $246.20   $246.20  
  Purchase #3 $237.94   9.297%   $260.0613   $260.06   $260.05   $260.10  
  Purchase #4 $61.29   10.742%   $67.8738   $67.87   $67.85   $67.90  
  Purchase #5 $250.59   3.778%   $260.0573   $260.06   $260.05   $260.10  
  Purchase #6 $248.58   10.406%   $274.4472   $274.45   $274.45   $274.40  
  Purchase #7 $121.98   9.666%   $133.7706   $133.77   $133.75   $133.80  
  7 purchase totals = $1,258.48       $1,365.5947   $1,365.60   $1,365.55   $1,365.70