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 $131.93   12.660%   $148.6323   $148.63   $148.65   $148.60  
  Purchase #2 $201.87   13.605%   $229.3344   $229.33   $229.35   $229.30  
  Purchase #3 $127.58   5.112%   $134.1019   $134.10   $134.10   $134.10  
  Purchase #4 $225.94   5.764%   $238.9632   $238.96   $238.95   $239.00  
  Purchase #5 $43.84   13.522%   $49.768   $49.77   $49.75   $49.80  
  Purchase #6 $88.94   10.254%   $98.0599   $98.06   $98.05   $98.10  
  Purchase #7 $148.28   9.314%   $162.0908   $162.09   $162.10   $162.10  
  7 purchase totals = $968.38       $1,060.9505   $1,060.94   $1,060.95   $1,061.00