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 $23.43   11.265%   $26.0694   $26.07   $26.05   $26.10  
  Purchase #2 $212.84   10.642%   $235.4904   $235.49   $235.50   $235.50  
  Purchase #3 $96.68   5.435%   $101.9346   $101.93   $101.95   $101.90  
  Purchase #4 $36.60   12.712%   $41.2526   $41.25   $41.25   $41.30  
  Purchase #5 $198.77   8.843%   $216.3472   $216.35   $216.35   $216.30  
  Purchase #6 $154.57   3.162%   $159.4575   $159.46   $159.45   $159.50  
  Purchase #7 $13.79   10.151%   $15.1898   $15.19   $15.20   $15.20  
  7 purchase totals = $736.68       $795.7415   $795.74   $795.75   $795.80