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 $94.35   4.293%   $98.4004   $98.40   $98.40   $98.40  
  Purchase #2 $244.59   4.216%   $254.9019   $254.90   $254.90   $254.90  
  Purchase #3 $9.34   10.463%   $10.3172   $10.32   $10.30   $10.30  
  Purchase #4 $102.61   7.339%   $110.1405   $110.14   $110.15   $110.10  
  Purchase #5 $189.78   4.743%   $198.7813   $198.78   $198.80   $198.80  
  Purchase #6 $228.94   7.803%   $246.8042   $246.80   $246.80   $246.80  
  Purchase #7 $32.91   9.599%   $36.069   $36.07   $36.05   $36.10  
  7 purchase totals = $902.52       $955.4145   $955.41   $955.40   $955.40