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 $65.69   12.605%   $73.9702   $73.97   $73.95   $74.00  
  Purchase #2 $32.55   10.613%   $36.0045   $36.00   $36.00   $36.00  
  Purchase #3 $18.86   4.445%   $19.6983   $19.70   $19.70   $19.70  
  Purchase #4 $194.99   6.264%   $207.2042   $207.20   $207.20   $207.20  
  Purchase #5 $160.59   7.501%   $172.6359   $172.64   $172.65   $172.60  
  Purchase #6 $141.65   8.688%   $153.9566   $153.96   $153.95   $154.00  
  Purchase #7 $201.68   6.109%   $214.0006   $214.00   $214.00   $214.00  
  7 purchase totals = $816.01       $877.4703   $877.47   $877.45   $877.50