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 $56.87   10.690%   $62.9494   $62.95   $62.95   $62.90  
  Purchase #2 $214.99   7.784%   $231.7248   $231.72   $231.70   $231.70  
  Purchase #3 $113.44   11.335%   $126.2984   $126.30   $126.30   $126.30  
  Purchase #4 $243.87   10.257%   $268.8837   $268.88   $268.90   $268.90  
  Purchase #5 $54.55   4.747%   $57.1395   $57.14   $57.15   $57.10  
  Purchase #6 $166.94   12.715%   $188.1664   $188.17   $188.15   $188.20  
  Purchase #7 $178.92   7.869%   $192.9992   $193.00   $193.00   $193.00  
  7 purchase totals = $1,029.58       $1,128.1614   $1,128.16   $1,128.15   $1,128.10