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 $216.93   7.419%   $233.024   $233.02   $233.00   $233.00  
  Purchase #2 $234.58   8.753%   $255.1128   $255.11   $255.10   $255.10  
  Purchase #3 $41.29   3.225%   $42.6216   $42.62   $42.60   $42.60  
  Purchase #4 $67.31   4.236%   $70.1613   $70.16   $70.15   $70.20  
  Purchase #5 $131.82   9.713%   $144.6237   $144.62   $144.60   $144.60  
  Purchase #6 $122.62   7.414%   $131.711   $131.71   $131.70   $131.70  
  Purchase #7 $220.62   7.280%   $236.6811   $236.68   $236.70   $236.70  
  7 purchase totals = $1,035.17       $1,113.9355   $1,113.92   $1,113.85   $1,113.90