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 $60.28   7.247%   $64.6485   $64.65   $64.65   $64.60  
  Purchase #2 $112.44   10.456%   $124.1967   $124.20   $124.20   $124.20  
  Purchase #3 $154.25   12.834%   $174.0464   $174.05   $174.05   $174.00  
  Purchase #4 $36.58   7.866%   $39.4574   $39.46   $39.45   $39.50  
  Purchase #5 $108.65   12.708%   $122.4572   $122.46   $122.45   $122.50  
  Purchase #6 $162.86   11.730%   $181.9635   $181.96   $181.95   $182.00  
  Purchase #7 $225.79   8.299%   $244.5283   $244.53   $244.55   $244.50  
  7 purchase totals = $860.85       $951.2980   $951.31   $951.30   $951.30