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 $232.25   10.544%   $256.7384   $256.74   $256.75   $256.70  
  Purchase #2 $126.51   7.211%   $135.6326   $135.63   $135.65   $135.60  
  Purchase #3 $196.69   5.686%   $207.8738   $207.87   $207.85   $207.90  
  Purchase #4 $108.46   4.647%   $113.5001   $113.50   $113.50   $113.50  
  Purchase #5 $185.74   5.671%   $196.2733   $196.27   $196.25   $196.30  
  Purchase #6 $165.96   5.349%   $174.8372   $174.84   $174.85   $174.80  
  Purchase #7 $39.85   4.513%   $41.6484   $41.65   $41.65   $41.60  
  7 purchase totals = $1,055.46       $1,126.5038   $1,126.50   $1,126.50   $1,126.40