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 $44.43   8.387%   $48.1563   $48.16   $48.15   $48.20  
  Purchase #2 $215.73   12.486%   $242.666   $242.67   $242.65   $242.70  
  Purchase #3 $200.76   7.177%   $215.1685   $215.17   $215.15   $215.20  
  Purchase #4 $132.80   12.670%   $149.6258   $149.63   $149.65   $149.60  
  Purchase #5 $205.79   8.567%   $223.42   $223.42   $223.40   $223.40  
  Purchase #6 $248.29   6.517%   $264.4711   $264.47   $264.45   $264.50  
  Purchase #7 $224.57   4.198%   $233.9974   $234.00   $234.00   $234.00  
  7 purchase totals = $1,272.37       $1,377.5051   $1,377.52   $1,377.45   $1,377.60