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 $208.27   3.578%   $215.7219   $215.72   $215.70   $215.70  
  Purchase #2 $211.65   5.102%   $222.4484   $222.45   $222.45   $222.40  
  Purchase #3 $65.45   8.650%   $71.1114   $71.11   $71.10   $71.10  
  Purchase #4 $226.86   3.823%   $235.5329   $235.53   $235.55   $235.50  
  Purchase #5 $69.68   6.243%   $74.0301   $74.03   $74.05   $74.00  
  Purchase #6 $181.29   5.140%   $190.6083   $190.61   $190.60   $190.60  
  Purchase #7 $88.47   6.395%   $94.1277   $94.13   $94.15   $94.10  
  7 purchase totals = $1,051.67       $1,103.5807   $1,103.58   $1,103.60   $1,103.40