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 $151.94   6.829%   $162.316   $162.32   $162.30   $162.30  
  Purchase #2 $213.91   4.436%   $223.399   $223.40   $223.40   $223.40  
  Purchase #3 $202.63   11.358%   $225.6447   $225.64   $225.65   $225.60  
  Purchase #4 $165.64   5.492%   $174.7369   $174.74   $174.75   $174.70  
  Purchase #5 $168.64   10.712%   $186.7047   $186.70   $186.70   $186.70  
  Purchase #6 $178.33   11.205%   $198.3119   $198.31   $198.30   $198.30  
  Purchase #7 $29.25   8.189%   $31.6453   $31.65   $31.65   $31.60  
  7 purchase totals = $1,110.34       $1,202.7585   $1,202.76   $1,202.75   $1,202.60