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 $118.27   11.615%   $132.0071   $132.01   $132.00   $132.00  
  Purchase #2 $245.34   5.224%   $258.1566   $258.16   $258.15   $258.20  
  Purchase #3 $151.36   7.870%   $163.272   $163.27   $163.25   $163.30  
  Purchase #4 $209.68   4.762%   $219.665   $219.67   $219.65   $219.70  
  Purchase #5 $61.91   9.656%   $67.888   $67.89   $67.90   $67.90  
  Purchase #6 $58.59   9.201%   $63.9809   $63.98   $64.00   $64.00  
  Purchase #7 $203.74   6.520%   $217.0238   $217.02   $217.00   $217.00  
  7 purchase totals = $1,048.89       $1,121.9934   $1,122.00   $1,121.95   $1,122.10