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 $84.87   13.147%   $96.0279   $96.03   $96.05   $96.00  
  Purchase #2 $232.35   13.331%   $263.3246   $263.32   $263.30   $263.30  
  Purchase #3 $86.74   7.305%   $93.0764   $93.08   $93.10   $93.10  
  Purchase #4 $23.66   3.169%   $24.4098   $24.41   $24.40   $24.40  
  Purchase #5 $206.28   8.272%   $223.3435   $223.34   $223.35   $223.30  
  Purchase #6 $78.81   12.143%   $88.3799   $88.38   $88.40   $88.40  
  Purchase #7 $68.93   9.460%   $75.4508   $75.45   $75.45   $75.50  
  7 purchase totals = $781.64       $864.0129   $864.01   $864.05   $864.00