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 $95.88   7.352%   $102.9291   $102.93   $102.95   $102.90  
  Purchase #2 $194.63   6.124%   $206.5491   $206.55   $206.55   $206.50  
  Purchase #3 $231.54   7.564%   $249.0537   $249.05   $249.05   $249.10  
  Purchase #4 $178.99   7.828%   $193.0013   $193.00   $193.00   $193.00  
  Purchase #5 $151.87   11.736%   $169.6935   $169.69   $169.70   $169.70  
  Purchase #6 $87.27   8.497%   $94.6853   $94.69   $94.70   $94.70  
  Purchase #7 $33.62   5.147%   $35.3504   $35.35   $35.35   $35.40  
  7 purchase totals = $973.80       $1,051.2624   $1,051.26   $1,051.30   $1,051.30