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 $69.61   4.605%   $72.8155   $72.82   $72.80   $72.80  
  Purchase #2 $219.64   13.673%   $249.6714   $249.67   $249.65   $249.70  
  Purchase #3 $216.38   3.829%   $224.6652   $224.67   $224.65   $224.70  
  Purchase #4 $239.28   13.855%   $272.4322   $272.43   $272.45   $272.40  
  Purchase #5 $208.38   6.412%   $221.7413   $221.74   $221.75   $221.70  
  Purchase #6 $134.62   5.554%   $142.0968   $142.10   $142.10   $142.10  
  Purchase #7 $18.58   12.605%   $20.922   $20.92   $20.90   $20.90  
  7 purchase totals = $1,106.49       $1,204.3444   $1,204.35   $1,204.30   $1,204.30