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 $161.45   8.558%   $175.2669   $175.27   $175.25   $175.30  
  Purchase #2 $214.85   8.263%   $232.6031   $232.60   $232.60   $232.60  
  Purchase #3 $64.99   10.307%   $71.6885   $71.69   $71.70   $71.70  
  Purchase #4 $146.95   3.752%   $152.4636   $152.46   $152.45   $152.50  
  Purchase #5 $45.87   3.764%   $47.5965   $47.60   $47.60   $47.60  
  Purchase #6 $124.45   12.659%   $140.2041   $140.20   $140.20   $140.20  
  Purchase #7 $226.85   8.244%   $245.5515   $245.55   $245.55   $245.60  
  7 purchase totals = $985.41       $1,065.3742   $1,065.37   $1,065.35   $1,065.50