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 $88.93   7.219%   $95.3499   $95.35   $95.35   $95.30  
  Purchase #2 $231.56   7.748%   $249.5013   $249.50   $249.50   $249.50  
  Purchase #3 $164.75   11.629%   $183.9088   $183.91   $183.90   $183.90  
  Purchase #4 $174.68   13.725%   $198.6548   $198.65   $198.65   $198.70  
  Purchase #5 $158.97   11.327%   $176.9765   $176.98   $177.00   $177.00  
  Purchase #6 $67.74   11.348%   $75.4271   $75.43   $75.45   $75.40  
  Purchase #7 $122.26   7.731%   $131.7119   $131.71   $131.70   $131.70  
  7 purchase totals = $1,008.89       $1,111.5303   $1,111.53   $1,111.55   $1,111.50