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 $62.64   10.404%   $69.1571   $69.16   $69.15   $69.20  
  Purchase #2 $79.76   11.236%   $88.7218   $88.72   $88.70   $88.70  
  Purchase #3 $171.36   8.772%   $186.3917   $186.39   $186.40   $186.40  
  Purchase #4 $244.38   10.342%   $269.6538   $269.65   $269.65   $269.70  
  Purchase #5 $207.54   12.338%   $233.1463   $233.15   $233.15   $233.10  
  Purchase #6 $134.49   8.411%   $145.802   $145.80   $145.80   $145.80  
  Purchase #7 $65.95   7.839%   $71.1198   $71.12   $71.10   $71.10  
  7 purchase totals = $966.12       $1,063.9925   $1,063.99   $1,063.95   $1,064.00