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 $214.77   9.259%   $234.6556   $234.66   $234.65   $234.70  
  Purchase #2 $216.33   8.413%   $234.5298   $234.53   $234.55   $234.50  
  Purchase #3 $160.96   6.418%   $171.2904   $171.29   $171.30   $171.30  
  Purchase #4 $114.67   5.420%   $120.8851   $120.89   $120.90   $120.90  
  Purchase #5 $181.50   10.617%   $200.7699   $200.77   $200.75   $200.80  
  Purchase #6 $203.59   6.572%   $216.9699   $216.97   $216.95   $217.00  
  Purchase #7 $76.45   8.118%   $82.6562   $82.66   $82.65   $82.70  
  7 purchase totals = $1,168.27       $1,261.7569   $1,261.77   $1,261.75   $1,261.90