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 $57.80   5.781%   $61.1414   $61.14   $61.15   $61.10  
  Purchase #2 $135.95   11.582%   $151.6957   $151.70   $151.70   $151.70  
  Purchase #3 $209.37   10.155%   $230.6315   $230.63   $230.65   $230.60  
  Purchase #4 $171.66   8.195%   $185.7275   $185.73   $185.75   $185.70  
  Purchase #5 $224.43   5.760%   $237.3572   $237.36   $237.35   $237.40  
  Purchase #6 $95.87   5.735%   $101.3681   $101.37   $101.35   $101.40  
  Purchase #7 $142.54   4.840%   $149.4389   $149.44   $149.45   $149.40  
  7 purchase totals = $1,037.62       $1,117.3603   $1,117.37   $1,117.40   $1,117.30