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 $61.28   9.515%   $67.1108   $67.11   $67.10   $67.10  
  Purchase #2 $197.35   4.540%   $206.3097   $206.31   $206.30   $206.30  
  Purchase #3 $127.64   10.456%   $140.986   $140.99   $141.00   $141.00  
  Purchase #4 $157.77   3.721%   $163.6406   $163.64   $163.65   $163.60  
  Purchase #5 $154.34   12.113%   $173.0352   $173.04   $173.05   $173.00  
  Purchase #6 $235.30   8.847%   $256.117   $256.12   $256.10   $256.10  
  Purchase #7 $44.29   5.212%   $46.5984   $46.60   $46.60   $46.60  
  7 purchase totals = $977.97       $1,053.7977   $1,053.81   $1,053.80   $1,053.70