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 $36.62   13.627%   $41.6102   $41.61   $41.60   $41.60  
  Purchase #2 $204.99   10.406%   $226.3213   $226.32   $226.30   $226.30  
  Purchase #3 $224.75   3.521%   $232.6634   $232.66   $232.65   $232.70  
  Purchase #4 $54.57   3.664%   $56.5694   $56.57   $56.55   $56.60  
  Purchase #5 $200.47   5.862%   $212.2216   $212.22   $212.20   $212.20  
  Purchase #6 $172.83   12.628%   $194.655   $194.66   $194.65   $194.70  
  Purchase #7 $75.89   10.526%   $83.8782   $83.88   $83.90   $83.90  
  7 purchase totals = $970.12       $1,047.9191   $1,047.92   $1,047.85   $1,048.00