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 $59.89   3.514%   $61.9945   $61.99   $62.00   $62.00  
  Purchase #2 $248.82   5.474%   $262.4404   $262.44   $262.45   $262.40  
  Purchase #3 $215.52   10.835%   $238.8716   $238.87   $238.85   $238.90  
  Purchase #4 $106.86   6.539%   $113.8476   $113.85   $113.85   $113.80  
  Purchase #5 $167.42   9.810%   $183.8439   $183.84   $183.85   $183.80  
  Purchase #6 $136.47   4.565%   $142.6999   $142.70   $142.70   $142.70  
  Purchase #7 $32.94   6.850%   $35.1964   $35.20   $35.20   $35.20  
  7 purchase totals = $967.92       $1,038.8943   $1,038.89   $1,038.90   $1,038.80