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 $208.61   8.578%   $226.5046   $226.50   $226.50   $226.50  
  Purchase #2 $78.71   9.375%   $86.0891   $86.09   $86.10   $86.10  
  Purchase #3 $226.33   8.356%   $245.2421   $245.24   $245.25   $245.20  
  Purchase #4 $67.78   11.713%   $75.7191   $75.72   $75.70   $75.70  
  Purchase #5 $60.53   7.107%   $64.8319   $64.83   $64.85   $64.80  
  Purchase #6 $228.36   10.181%   $251.6093   $251.61   $251.60   $251.60  
  Purchase #7 $162.55   7.616%   $174.9298   $174.93   $174.95   $174.90  
  7 purchase totals = $1,032.87       $1,124.9259   $1,124.92   $1,124.95   $1,124.80