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 $92.67   5.246%   $97.5315   $97.53   $97.55   $97.50  
  Purchase #2 $108.44   10.465%   $119.7882   $119.79   $119.80   $119.80  
  Purchase #3 $221.58   8.619%   $240.678   $240.68   $240.70   $240.70  
  Purchase #4 $217.41   7.331%   $233.3483   $233.35   $233.35   $233.30  
  Purchase #5 $179.89   7.324%   $193.0651   $193.07   $193.05   $193.10  
  Purchase #6 $83.87   8.190%   $90.739   $90.74   $90.75   $90.70  
  Purchase #7 $108.42   10.859%   $120.1933   $120.19   $120.20   $120.20  
  7 purchase totals = $1,012.28       $1,095.3434   $1,095.35   $1,095.40   $1,095.30