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 $196.42   5.396%   $207.0188   $207.02   $207.00   $207.00  
  Purchase #2 $43.76   3.450%   $45.2697   $45.27   $45.25   $45.30  
  Purchase #3 $181.49   8.860%   $197.57   $197.57   $197.55   $197.60  
  Purchase #4 $103.51   6.210%   $109.938   $109.94   $109.95   $109.90  
  Purchase #5 $208.84   8.581%   $226.7606   $226.76   $226.75   $226.80  
  Purchase #6 $109.65   9.236%   $119.7773   $119.78   $119.80   $119.80  
  Purchase #7 $208.72   8.659%   $226.7931   $226.79   $226.80   $226.80  
  7 purchase totals = $1,052.39       $1,133.1275   $1,133.13   $1,133.10   $1,133.20