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 $118.68   6.552%   $126.4559   $126.46   $126.45   $126.50  
  Purchase #2 $230.83   4.535%   $241.2981   $241.30   $241.30   $241.30  
  Purchase #3 $76.25   8.128%   $82.4476   $82.45   $82.45   $82.40  
  Purchase #4 $140.59   4.790%   $147.3243   $147.32   $147.30   $147.30  
  Purchase #5 $46.96   10.484%   $51.8833   $51.88   $51.90   $51.90  
  Purchase #6 $232.60   6.388%   $247.4585   $247.46   $247.45   $247.50  
  Purchase #7 $47.89   3.169%   $49.4076   $49.41   $49.40   $49.40  
  7 purchase totals = $893.80       $946.2753   $946.28   $946.25   $946.30