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 $114.72   10.302%   $126.5385   $126.54   $126.55   $126.50  
  Purchase #2 $14.96   10.597%   $16.5453   $16.55   $16.55   $16.50  
  Purchase #3 $201.41   12.330%   $226.2439   $226.24   $226.25   $226.20  
  Purchase #4 $163.38   13.690%   $185.7467   $185.75   $185.75   $185.70  
  Purchase #5 $172.74   5.401%   $182.0697   $182.07   $182.05   $182.10  
  Purchase #6 $227.29   8.566%   $246.7597   $246.76   $246.75   $246.80  
  Purchase #7 $113.47   6.211%   $120.5176   $120.52   $120.50   $120.50  
  7 purchase totals = $1,007.97       $1,104.4214   $1,104.43   $1,104.40   $1,104.30