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 $63.86   10.709%   $70.6988   $70.70   $70.70   $70.70  
  Purchase #2 $223.60   9.103%   $243.9543   $243.95   $243.95   $244.00  
  Purchase #3 $69.54   4.586%   $72.7291   $72.73   $72.75   $72.70  
  Purchase #4 $225.59   3.254%   $232.9307   $232.93   $232.95   $232.90  
  Purchase #5 $190.62   3.426%   $197.1506   $197.15   $197.15   $197.20  
  Purchase #6 $167.79   4.211%   $174.8556   $174.86   $174.85   $174.90  
  Purchase #7 $99.80   4.457%   $104.2481   $104.25   $104.25   $104.20  
  7 purchase totals = $1,040.80       $1,096.5672   $1,096.57   $1,096.60   $1,096.60