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 $59.94   11.253%   $66.685   $66.69   $66.70   $66.70  
  Purchase #2 $100.44   7.568%   $108.0413   $108.04   $108.05   $108.00  
  Purchase #3 $247.83   4.418%   $258.7791   $258.78   $258.80   $258.80  
  Purchase #4 $175.43   6.395%   $186.6487   $186.65   $186.65   $186.60  
  Purchase #5 $46.50   13.665%   $52.8542   $52.85   $52.85   $52.90  
  Purchase #6 $22.73   3.448%   $23.5137   $23.51   $23.50   $23.50  
  Purchase #7 $178.50   11.214%   $198.517   $198.52   $198.50   $198.50  
  7 purchase totals = $831.37       $895.0390   $895.04   $895.05   $895.00