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 $92.51   4.524%   $96.6952   $96.70   $96.70   $96.70  
  Purchase #2 $149.48   4.663%   $156.4503   $156.45   $156.45   $156.50  
  Purchase #3 $24.28   12.207%   $27.2439   $27.24   $27.25   $27.20  
  Purchase #4 $16.98   12.405%   $19.0864   $19.09   $19.10   $19.10  
  Purchase #5 $213.62   7.488%   $229.6159   $229.62   $229.60   $229.60  
  Purchase #6 $149.74   6.314%   $159.1946   $159.19   $159.20   $159.20  
  Purchase #7 $233.87   5.747%   $247.3105   $247.31   $247.30   $247.30  
  7 purchase totals = $880.48       $935.5968   $935.60   $935.60   $935.60