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 $14.41   3.676%   $14.9397   $14.94   $14.95   $14.90  
  Purchase #2 $161.39   8.190%   $174.6078   $174.61   $174.60   $174.60  
  Purchase #3 $126.57   6.559%   $134.8717   $134.87   $134.85   $134.90  
  Purchase #4 $168.53   5.486%   $177.7756   $177.78   $177.80   $177.80  
  Purchase #5 $22.72   13.845%   $25.8656   $25.87   $25.85   $25.90  
  Purchase #6 $154.85   4.163%   $161.2964   $161.30   $161.30   $161.30  
  Purchase #7 $83.78   3.835%   $86.993   $86.99   $87.00   $87.00  
  7 purchase totals = $732.25       $776.3498   $776.36   $776.35   $776.40