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 $195.69   8.407%   $212.1417   $212.14   $212.15   $212.10  
  Purchase #2 $89.98   6.302%   $95.6505   $95.65   $95.65   $95.70  
  Purchase #3 $120.98   6.663%   $129.0409   $129.04   $129.05   $129.00  
  Purchase #4 $54.81   10.655%   $60.65   $60.65   $60.65   $60.70  
  Purchase #5 $244.77   3.170%   $252.5292   $252.53   $252.55   $252.50  
  Purchase #6 $244.72   6.190%   $259.8682   $259.87   $259.85   $259.90  
  Purchase #7 $180.65   8.807%   $196.5598   $196.56   $196.55   $196.60  
  7 purchase totals = $1,131.60       $1,206.4403   $1,206.44   $1,206.45   $1,206.50