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 $67.50   3.134%   $69.6155   $69.62   $69.60   $69.60  
  Purchase #2 $218.46   11.187%   $242.8991   $242.90   $242.90   $242.90  
  Purchase #3 $42.50   6.485%   $45.2561   $45.26   $45.25   $45.30  
  Purchase #4 $237.62   7.352%   $255.0898   $255.09   $255.10   $255.10  
  Purchase #5 $156.51   9.706%   $171.7009   $171.70   $171.70   $171.70  
  Purchase #6 $61.72   5.643%   $65.2029   $65.20   $65.20   $65.20  
  Purchase #7 $198.63   10.842%   $220.1655   $220.17   $220.15   $220.20  
  7 purchase totals = $982.94       $1,069.9298   $1,069.94   $1,069.90   $1,070.00