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 $117.74   7.386%   $126.4363   $126.44   $126.45   $126.40  
  Purchase #2 $114.42   4.705%   $119.8035   $119.80   $119.80   $119.80  
  Purchase #3 $43.77   7.277%   $46.9551   $46.96   $46.95   $47.00  
  Purchase #4 $207.76   5.384%   $218.9458   $218.95   $218.95   $218.90  
  Purchase #5 $111.76   11.591%   $124.7141   $124.71   $124.70   $124.70  
  Purchase #6 $236.47   13.200%   $267.684   $267.68   $267.70   $267.70  
  Purchase #7 $94.96   8.355%   $102.8939   $102.89   $102.90   $102.90  
  7 purchase totals = $926.88       $1,007.4327   $1,007.43   $1,007.45   $1,007.40