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 $60.63   11.451%   $67.5727   $67.57   $67.55   $67.60  
  Purchase #2 $90.59   6.443%   $96.4267   $96.43   $96.45   $96.40  
  Purchase #3 $79.77   6.202%   $84.7173   $84.72   $84.70   $84.70  
  Purchase #4 $67.75   6.213%   $71.9593   $71.96   $71.95   $72.00  
  Purchase #5 $106.91   8.139%   $115.6114   $115.61   $115.60   $115.60  
  Purchase #6 $135.37   9.537%   $148.2802   $148.28   $148.30   $148.30  
  Purchase #7 $168.67   4.568%   $176.3748   $176.37   $176.35   $176.40  
  7 purchase totals = $709.69       $760.9424   $760.94   $760.90   $761.00