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 $56.60   7.792%   $61.0103   $61.01   $61.00   $61.00  
  Purchase #2 $176.70   13.221%   $200.0615   $200.06   $200.05   $200.10  
  Purchase #3 $80.71   4.400%   $84.2612   $84.26   $84.25   $84.30  
  Purchase #4 $193.37   8.244%   $209.3114   $209.31   $209.30   $209.30  
  Purchase #5 $223.40   7.632%   $240.4499   $240.45   $240.45   $240.40  
  Purchase #6 $157.70   13.291%   $178.6599   $178.66   $178.65   $178.70  
  Purchase #7 $171.74   4.774%   $179.9389   $179.94   $179.95   $179.90  
  7 purchase totals = $1,060.22       $1,153.6931   $1,153.69   $1,153.65   $1,153.70