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 $86.25   8.541%   $93.6166   $93.62   $93.60   $93.60  
  Purchase #2 $197.37   3.102%   $203.4924   $203.49   $203.50   $203.50  
  Purchase #3 $134.29   13.273%   $152.1143   $152.11   $152.10   $152.10  
  Purchase #4 $104.63   5.585%   $110.4736   $110.47   $110.45   $110.50  
  Purchase #5 $48.95   13.739%   $55.6752   $55.68   $55.70   $55.70  
  Purchase #6 $171.89   6.425%   $182.9339   $182.93   $182.95   $182.90  
  Purchase #7 $225.37   8.264%   $243.9946   $243.99   $244.00   $244.00  
  7 purchase totals = $968.75       $1,042.3006   $1,042.29   $1,042.30   $1,042.30