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 $105.95   6.265%   $112.5878   $112.59   $112.60   $112.60  
  Purchase #2 $148.96   8.615%   $161.7929   $161.79   $161.80   $161.80  
  Purchase #3 $195.36   6.309%   $207.6853   $207.69   $207.70   $207.70  
  Purchase #4 $79.35   12.835%   $89.5346   $89.53   $89.55   $89.50  
  Purchase #5 $61.49   6.813%   $65.6793   $65.68   $65.70   $65.70  
  Purchase #6 $238.99   13.641%   $271.5906   $271.59   $271.60   $271.60  
  Purchase #7 $153.80   6.303%   $163.494   $163.49   $163.50   $163.50  
  7 purchase totals = $983.90       $1,072.3645   $1,072.36   $1,072.45   $1,072.40