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 $141.51   8.498%   $153.5355   $153.54   $153.55   $153.50  
  Purchase #2 $222.69   10.543%   $246.1682   $246.17   $246.15   $246.20  
  Purchase #3 $203.50   7.454%   $218.6689   $218.67   $218.65   $218.70  
  Purchase #4 $107.67   8.253%   $116.556   $116.56   $116.55   $116.60  
  Purchase #5 $150.43   13.718%   $171.066   $171.07   $171.05   $171.10  
  Purchase #6 $108.80   8.368%   $117.9044   $117.90   $117.90   $117.90  
  Purchase #7 $94.93   8.208%   $102.7219   $102.72   $102.70   $102.70  
  7 purchase totals = $1,029.53       $1,126.6209   $1,126.63   $1,126.55   $1,126.70