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 $43.62   5.305%   $45.934   $45.93   $45.95   $45.90  
  Purchase #2 $108.69   11.573%   $121.2687   $121.27   $121.25   $121.30  
  Purchase #3 $30.32   11.679%   $33.8611   $33.86   $33.85   $33.90  
  Purchase #4 $161.48   6.347%   $171.7291   $171.73   $171.75   $171.70  
  Purchase #5 $214.55   11.469%   $239.1567   $239.16   $239.15   $239.20  
  Purchase #6 $31.87   9.577%   $34.9222   $34.92   $34.90   $34.90  
  Purchase #7 $110.77   5.398%   $116.7494   $116.75   $116.75   $116.70  
  7 purchase totals = $701.30       $763.6212   $763.62   $763.60   $763.60