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 $69.32   7.687%   $74.6486   $74.65   $74.65   $74.60  
  Purchase #2 $18.33   8.515%   $19.8908   $19.89   $19.90   $19.90  
  Purchase #3 $197.86   11.126%   $219.8739   $219.87   $219.85   $219.90  
  Purchase #4 $88.73   4.706%   $92.9056   $92.91   $92.90   $92.90  
  Purchase #5 $159.87   8.783%   $173.9114   $173.91   $173.90   $173.90  
  Purchase #6 $196.60   6.741%   $209.8528   $209.85   $209.85   $209.90  
  Purchase #7 $248.77   3.351%   $257.1063   $257.11   $257.10   $257.10  
  7 purchase totals = $979.48       $1,048.1894   $1,048.19   $1,048.15   $1,048.20