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 $217.80   3.604%   $225.6495   $225.65   $225.65   $225.60  
  Purchase #2 $110.68   5.406%   $116.6634   $116.66   $116.65   $116.70  
  Purchase #3 $22.66   8.596%   $24.6079   $24.61   $24.60   $24.60  
  Purchase #4 $175.83   4.542%   $183.8162   $183.82   $183.80   $183.80  
  Purchase #5 $193.44   10.858%   $214.4437   $214.44   $214.45   $214.40  
  Purchase #6 $186.86   11.132%   $207.6613   $207.66   $207.65   $207.70  
  Purchase #7 $211.61   5.621%   $223.5046   $223.50   $223.50   $223.50  
  7 purchase totals = $1,118.88       $1,196.3466   $1,196.34   $1,196.30   $1,196.30