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 $60.26   4.585%   $63.0229   $63.02   $63.00   $63.00  
  Purchase #2 $113.59   5.369%   $119.6886   $119.69   $119.70   $119.70  
  Purchase #3 $195.42   4.737%   $204.677   $204.68   $204.70   $204.70  
  Purchase #4 $215.64   10.652%   $238.61   $238.61   $238.60   $238.60  
  Purchase #5 $167.41   11.366%   $186.4378   $186.44   $186.45   $186.40  
  Purchase #6 $232.51   4.753%   $243.5612   $243.56   $243.55   $243.60  
  Purchase #7 $223.36   12.823%   $252.0015   $252.00   $252.00   $252.00  
  7 purchase totals = $1,208.19       $1,307.9990   $1,308.00   $1,308.00   $1,308.00