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 $188.86   8.872%   $205.6157   $205.62   $205.60   $205.60  
  Purchase #2 $52.58   8.451%   $57.0235   $57.02   $57.00   $57.00  
  Purchase #3 $114.74   8.671%   $124.6891   $124.69   $124.70   $124.70  
  Purchase #4 $163.29   11.192%   $181.5654   $181.57   $181.55   $181.60  
  Purchase #5 $170.86   4.812%   $179.0818   $179.08   $179.10   $179.10  
  Purchase #6 $211.37   6.405%   $224.9082   $224.91   $224.90   $224.90  
  Purchase #7 $121.68   8.501%   $132.024   $132.02   $132.00   $132.00  
  7 purchase totals = $1,023.38       $1,104.9077   $1,104.91   $1,104.85   $1,104.90