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 $56.72   9.553%   $62.1385   $62.14   $62.15   $62.10  
  Purchase #2 $211.97   6.870%   $226.5323   $226.53   $226.55   $226.50  
  Purchase #3 $216.58   8.637%   $235.286   $235.29   $235.30   $235.30  
  Purchase #4 $243.57   11.830%   $272.3843   $272.38   $272.40   $272.40  
  Purchase #5 $16.99   5.477%   $17.9205   $17.92   $17.90   $17.90  
  Purchase #6 $104.64   9.611%   $114.697   $114.70   $114.70   $114.70  
  Purchase #7 $100.86   3.557%   $104.4476   $104.45   $104.45   $104.40  
  7 purchase totals = $951.33       $1,033.4062   $1,033.41   $1,033.45   $1,033.30