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 $62.46   11.603%   $69.7072   $69.71   $69.70   $69.70  
  Purchase #2 $154.60   8.470%   $167.6946   $167.69   $167.70   $167.70  
  Purchase #3 $150.37   13.331%   $170.4158   $170.42   $170.40   $170.40  
  Purchase #4 $69.55   4.243%   $72.501   $72.50   $72.50   $72.50  
  Purchase #5 $65.78   3.280%   $67.9376   $67.94   $67.95   $67.90  
  Purchase #6 $169.66   10.378%   $187.2673   $187.27   $187.25   $187.30  
  Purchase #7 $218.95   5.851%   $231.7608   $231.76   $231.75   $231.80  
  7 purchase totals = $891.37       $967.2843   $967.29   $967.25   $967.30