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 $54.66   12.542%   $61.5155   $61.52   $61.50   $61.50  
  Purchase #2 $236.32   10.187%   $260.3939   $260.39   $260.40   $260.40  
  Purchase #3 $213.79   11.697%   $238.797   $238.80   $238.80   $238.80  
  Purchase #4 $189.39   7.652%   $203.8821   $203.88   $203.90   $203.90  
  Purchase #5 $19.76   12.555%   $22.2409   $22.24   $22.25   $22.20  
  Purchase #6 $125.67   8.435%   $136.2703   $136.27   $136.25   $136.30  
  Purchase #7 $161.92   7.307%   $173.7515   $173.75   $173.75   $173.80  
  7 purchase totals = $1,001.51       $1,096.8512   $1,096.85   $1,096.85   $1,096.90