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 $113.95   3.660%   $118.1206   $118.12   $118.10   $118.10  
  Purchase #2 $125.81   11.650%   $140.4669   $140.47   $140.45   $140.50  
  Purchase #3 $137.59   4.640%   $143.9742   $143.97   $143.95   $144.00  
  Purchase #4 $92.70   3.649%   $96.0826   $96.08   $96.10   $96.10  
  Purchase #5 $160.95   5.406%   $169.651   $169.65   $169.65   $169.70  
  Purchase #6 $207.41   13.202%   $234.7923   $234.79   $234.80   $234.80  
  Purchase #7 $114.27   4.762%   $119.7115   $119.71   $119.70   $119.70  
  7 purchase totals = $952.68       $1,022.7991   $1,022.79   $1,022.75   $1,022.90