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 $213.55   4.352%   $222.8437   $222.84   $222.85   $222.80  
  Purchase #2 $242.39   11.261%   $269.6855   $269.69   $269.70   $269.70  
  Purchase #3 $161.69   8.812%   $175.9381   $175.94   $175.95   $175.90  
  Purchase #4 $161.37   13.712%   $183.4971   $183.50   $183.50   $183.50  
  Purchase #5 $169.77   4.266%   $177.0124   $177.01   $177.00   $177.00  
  Purchase #6 $185.93   4.352%   $194.0217   $194.02   $194.00   $194.00  
  Purchase #7 $241.63   7.227%   $259.0926   $259.09   $259.10   $259.10  
  7 purchase totals = $1,376.33       $1,482.0911   $1,482.09   $1,482.10   $1,482.00