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 $171.77   7.485%   $184.627   $184.63   $184.65   $184.60  
  Purchase #2 $159.99   7.440%   $171.8933   $171.89   $171.90   $171.90  
  Purchase #3 $119.91   12.248%   $134.5966   $134.60   $134.60   $134.60  
  Purchase #4 $184.90   6.133%   $196.2399   $196.24   $196.25   $196.20  
  Purchase #5 $160.66   10.168%   $176.9959   $177.00   $177.00   $177.00  
  Purchase #6 $135.26   5.285%   $142.4085   $142.41   $142.40   $142.40  
  Purchase #7 $223.36   9.434%   $244.4318   $244.43   $244.45   $244.40  
  7 purchase totals = $1,155.85       $1,251.1930   $1,251.20   $1,251.25   $1,251.10