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 $50.27   9.206%   $54.8979   $54.90   $54.90   $54.90  
  Purchase #2 $124.88   9.687%   $136.9771   $136.98   $137.00   $137.00  
  Purchase #3 $163.26   12.338%   $183.403   $183.40   $183.40   $183.40  
  Purchase #4 $88.71   11.656%   $99.05   $99.05   $99.05   $99.10  
  Purchase #5 $148.86   5.297%   $156.7451   $156.75   $156.75   $156.70  
  Purchase #6 $240.46   10.377%   $265.4125   $265.41   $265.40   $265.40  
  Purchase #7 $167.63   4.433%   $175.061   $175.06   $175.05   $175.10  
  7 purchase totals = $984.07       $1,071.5466   $1,071.55   $1,071.55   $1,071.60