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 $96.71   10.677%   $107.0357   $107.04   $107.05   $107.00  
  Purchase #2 $220.28   4.269%   $229.6838   $229.68   $229.70   $229.70  
  Purchase #3 $165.41   8.570%   $179.5856   $179.59   $179.60   $179.60  
  Purchase #4 $237.61   5.844%   $251.4959   $251.50   $251.50   $251.50  
  Purchase #5 $169.68   4.512%   $177.336   $177.34   $177.35   $177.30  
  Purchase #6 $119.66   5.265%   $125.9601   $125.96   $125.95   $126.00  
  Purchase #7 $88.80   5.269%   $93.4789   $93.48   $93.50   $93.50  
  7 purchase totals = $1,098.15       $1,164.5760   $1,164.59   $1,164.65   $1,164.60