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 $232.83   13.837%   $265.0467   $265.05   $265.05   $265.00  
  Purchase #2 $58.43   8.281%   $63.2686   $63.27   $63.25   $63.30  
  Purchase #3 $68.37   8.148%   $73.9408   $73.94   $73.95   $73.90  
  Purchase #4 $171.29   9.344%   $187.2953   $187.30   $187.30   $187.30  
  Purchase #5 $211.76   11.304%   $235.6974   $235.70   $235.70   $235.70  
  Purchase #6 $230.64   13.671%   $262.1708   $262.17   $262.15   $262.20  
  Purchase #7 $240.72   7.131%   $257.8857   $257.89   $257.90   $257.90  
  7 purchase totals = $1,214.04       $1,345.3053   $1,345.32   $1,345.30   $1,345.30