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 $101.70   12.623%   $114.5376   $114.54   $114.55   $114.50  
  Purchase #2 $242.64   6.265%   $257.8414   $257.84   $257.85   $257.80  
  Purchase #3 $40.92   8.308%   $44.3196   $44.32   $44.30   $44.30  
  Purchase #4 $39.25   12.483%   $44.1496   $44.15   $44.15   $44.10  
  Purchase #5 $181.39   11.136%   $201.5896   $201.59   $201.60   $201.60  
  Purchase #6 $191.85   5.700%   $202.7855   $202.79   $202.80   $202.80  
  Purchase #7 $163.71   12.146%   $183.5942   $183.59   $183.60   $183.60  
  7 purchase totals = $961.46       $1,048.8175   $1,048.82   $1,048.85   $1,048.70