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 $86.48   10.571%   $95.6218   $95.62   $95.60   $95.60  
  Purchase #2 $32.75   5.472%   $34.5421   $34.54   $34.55   $34.50  
  Purchase #3 $230.81   4.208%   $240.5225   $240.52   $240.50   $240.50  
  Purchase #4 $159.75   5.691%   $168.8414   $168.84   $168.85   $168.80  
  Purchase #5 $248.42   13.392%   $281.6884   $281.69   $281.70   $281.70  
  Purchase #6 $159.59   5.720%   $168.7185   $168.72   $168.70   $168.70  
  Purchase #7 $202.57   5.282%   $213.2697   $213.27   $213.25   $213.30  
  7 purchase totals = $1,120.37       $1,203.2044   $1,203.20   $1,203.15   $1,203.10