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 $230.81   7.521%   $248.1692   $248.17   $248.15   $248.20  
  Purchase #2 $43.84   13.350%   $49.6926   $49.69   $49.70   $49.70  
  Purchase #3 $84.80   13.435%   $96.1929   $96.19   $96.20   $96.20  
  Purchase #4 $163.76   6.621%   $174.6025   $174.60   $174.60   $174.60  
  Purchase #5 $9.80   4.102%   $10.202   $10.20   $10.20   $10.20  
  Purchase #6 $152.27   5.845%   $161.1702   $161.17   $161.15   $161.20  
  Purchase #7 $201.68   6.400%   $214.5875   $214.59   $214.60   $214.60  
  7 purchase totals = $886.96       $954.6169   $954.61   $954.60   $954.70