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 $237.94   11.372%   $264.9985   $265.00   $265.00   $265.00  
  Purchase #2 $218.79   3.784%   $227.069   $227.07   $227.05   $227.10  
  Purchase #3 $117.98   6.706%   $125.8917   $125.89   $125.90   $125.90  
  Purchase #4 $69.79   4.543%   $72.9606   $72.96   $72.95   $73.00  
  Purchase #5 $58.66   9.861%   $64.4445   $64.44   $64.45   $64.40  
  Purchase #6 $236.95   10.110%   $260.9056   $260.91   $260.90   $260.90  
  Purchase #7 $105.47   7.869%   $113.7694   $113.77   $113.75   $113.80  
  7 purchase totals = $1,045.58       $1,130.0393   $1,130.04   $1,130.00   $1,130.10