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 $232.68   8.596%   $252.6812   $252.68   $252.70   $252.70  
  Purchase #2 $195.32   8.445%   $211.8148   $211.81   $211.80   $211.80  
  Purchase #3 $74.42   6.530%   $79.2796   $79.28   $79.30   $79.30  
  Purchase #4 $234.67   3.339%   $242.5056   $242.51   $242.50   $242.50  
  Purchase #5 $196.59   4.301%   $205.0453   $205.05   $205.05   $205.00  
  Purchase #6 $56.94   3.110%   $58.7108   $58.71   $58.70   $58.70  
  Purchase #7 $190.77   6.393%   $202.9659   $202.97   $202.95   $203.00  
  7 purchase totals = $1,181.39       $1,253.0032   $1,253.01   $1,253.00   $1,253.00