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 $193.71   4.253%   $201.9485   $201.95   $201.95   $201.90  
  Purchase #2 $13.55   4.391%   $14.145   $14.15   $14.15   $14.10  
  Purchase #3 $182.42   11.377%   $203.1739   $203.17   $203.15   $203.20  
  Purchase #4 $46.65   5.653%   $49.2871   $49.29   $49.30   $49.30  
  Purchase #5 $17.43   6.827%   $18.6199   $18.62   $18.60   $18.60  
  Purchase #6 $59.83   11.644%   $66.7966   $66.80   $66.80   $66.80  
  Purchase #7 $64.79   8.177%   $70.0879   $70.09   $70.10   $70.10  
  7 purchase totals = $578.38       $624.0589   $624.07   $624.05   $624.00