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 $64.41   13.262%   $72.9521   $72.95   $72.95   $73.00  
  Purchase #2 $66.90   3.187%   $69.0321   $69.03   $69.05   $69.00  
  Purchase #3 $245.47   9.118%   $267.852   $267.85   $267.85   $267.90  
  Purchase #4 $16.30   4.601%   $17.05   $17.05   $17.05   $17.10  
  Purchase #5 $107.79   4.669%   $112.8227   $112.82   $112.80   $112.80  
  Purchase #6 $39.83   10.752%   $44.1125   $44.11   $44.10   $44.10  
  Purchase #7 $159.60   9.614%   $174.9439   $174.94   $174.95   $174.90  
  7 purchase totals = $700.30       $758.7653   $758.75   $758.75   $758.80