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 $59.73   6.565%   $63.6513   $63.65   $63.65   $63.70  
  Purchase #2 $130.78   7.432%   $140.4996   $140.50   $140.50   $140.50  
  Purchase #3 $97.73   7.141%   $104.7089   $104.71   $104.70   $104.70  
  Purchase #4 $54.54   4.437%   $56.9599   $56.96   $56.95   $57.00  
  Purchase #5 $80.73   6.687%   $86.1284   $86.13   $86.15   $86.10  
  Purchase #6 $84.98   3.143%   $87.6509   $87.65   $87.65   $87.70  
  Purchase #7 $225.54   11.523%   $251.529   $251.53   $251.55   $251.50  
  7 purchase totals = $734.03       $791.1280   $791.13   $791.15   $791.20