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 $222.60   9.464%   $243.6669   $243.67   $243.65   $243.70  
  Purchase #2 $247.33   8.807%   $269.1124   $269.11   $269.10   $269.10  
  Purchase #3 $165.41   5.721%   $174.8731   $174.87   $174.85   $174.90  
  Purchase #4 $203.90   6.686%   $217.5328   $217.53   $217.55   $217.50  
  Purchase #5 $140.44   8.681%   $152.6316   $152.63   $152.65   $152.60  
  Purchase #6 $233.94   11.398%   $260.6045   $260.60   $260.60   $260.60  
  Purchase #7 $162.29   3.210%   $167.4995   $167.50   $167.50   $167.50  
  7 purchase totals = $1,375.91       $1,485.9208   $1,485.91   $1,485.90   $1,485.90