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 $83.69   13.529%   $95.0124   $95.01   $95.00   $95.00  
  Purchase #2 $197.92   4.386%   $206.6008   $206.60   $206.60   $206.60  
  Purchase #3 $72.53   11.284%   $80.7143   $80.71   $80.70   $80.70  
  Purchase #4 $220.86   13.559%   $250.8064   $250.81   $250.80   $250.80  
  Purchase #5 $80.77   4.353%   $84.2859   $84.29   $84.30   $84.30  
  Purchase #6 $247.60   8.476%   $268.5866   $268.59   $268.60   $268.60  
  Purchase #7 $211.86   11.606%   $236.4485   $236.45   $236.45   $236.40  
  7 purchase totals = $1,115.23       $1,222.4549   $1,222.46   $1,222.45   $1,222.40