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 $10.72   6.762%   $11.4449   $11.44   $11.45   $11.40  
  Purchase #2 $87.83   8.137%   $94.9767   $94.98   $95.00   $95.00  
  Purchase #3 $78.99   5.616%   $83.4261   $83.43   $83.45   $83.40  
  Purchase #4 $201.28   4.386%   $210.1081   $210.11   $210.10   $210.10  
  Purchase #5 $15.59   3.793%   $16.1813   $16.18   $16.20   $16.20  
  Purchase #6 $128.38   12.862%   $144.8922   $144.89   $144.90   $144.90  
  Purchase #7 $240.83   9.626%   $264.0123   $264.01   $264.00   $264.00  
  7 purchase totals = $763.62       $825.0416   $825.04   $825.10   $825.00