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 $182.55   13.173%   $206.5973   $206.60   $206.60   $206.60  
  Purchase #2 $157.74   11.383%   $175.6955   $175.70   $175.70   $175.70  
  Purchase #3 $11.61   6.858%   $12.4062   $12.41   $12.40   $12.40  
  Purchase #4 $45.28   6.721%   $48.3233   $48.32   $48.30   $48.30  
  Purchase #5 $17.78   13.645%   $20.2061   $20.21   $20.20   $20.20  
  Purchase #6 $219.78   12.543%   $247.347   $247.35   $247.35   $247.30  
  Purchase #7 $236.38   6.280%   $251.2247   $251.22   $251.20   $251.20  
  7 purchase totals = $871.12       $961.8001   $961.81   $961.75   $961.70