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 $72.43   3.611%   $75.0454   $75.05   $75.05   $75.00  
  Purchase #2 $126.49   12.468%   $142.2608   $142.26   $142.25   $142.30  
  Purchase #3 $155.78   11.672%   $173.9626   $173.96   $173.95   $174.00  
  Purchase #4 $178.87   8.286%   $193.6912   $193.69   $193.70   $193.70  
  Purchase #5 $198.27   9.476%   $217.0581   $217.06   $217.05   $217.10  
  Purchase #6 $86.36   12.641%   $97.2768   $97.28   $97.30   $97.30  
  Purchase #7 $220.81   6.506%   $235.1759   $235.18   $235.20   $235.20  
  7 purchase totals = $1,039.01       $1,134.4708   $1,134.48   $1,134.50   $1,134.60