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 $41.95   3.872%   $43.5743   $43.57   $43.55   $43.60  
  Purchase #2 $155.57   6.612%   $165.8563   $165.86   $165.85   $165.90  
  Purchase #3 $210.89   12.353%   $236.9412   $236.94   $236.95   $236.90  
  Purchase #4 $65.74   13.424%   $74.5649   $74.56   $74.55   $74.60  
  Purchase #5 $213.46   10.407%   $235.6748   $235.67   $235.65   $235.70  
  Purchase #6 $86.48   13.603%   $98.2439   $98.24   $98.25   $98.20  
  Purchase #7 $218.55   4.456%   $228.2886   $228.29   $228.30   $228.30  
  7 purchase totals = $992.64       $1,083.1440   $1,083.13   $1,083.10   $1,083.20