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 $88.25   8.285%   $95.5615   $95.56   $95.55   $95.60  
  Purchase #2 $163.99   6.375%   $174.4444   $174.44   $174.45   $174.40  
  Purchase #3 $26.90   10.737%   $29.7883   $29.79   $29.80   $29.80  
  Purchase #4 $180.95   5.590%   $191.0651   $191.07   $191.05   $191.10  
  Purchase #5 $210.95   3.798%   $218.9619   $218.96   $218.95   $219.00  
  Purchase #6 $237.25   11.270%   $263.9881   $263.99   $264.00   $264.00  
  Purchase #7 $171.92   8.647%   $186.7859   $186.79   $186.80   $186.80  
  7 purchase totals = $1,080.21       $1,160.5952   $1,160.60   $1,160.60   $1,160.70