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 $57.80   10.214%   $63.7037   $63.70   $63.70   $63.70  
  Purchase #2 $168.30   8.210%   $182.1174   $182.12   $182.10   $182.10  
  Purchase #3 $249.81   6.301%   $265.5505   $265.55   $265.55   $265.60  
  Purchase #4 $118.60   3.543%   $122.802   $122.80   $122.80   $122.80  
  Purchase #5 $64.82   7.729%   $69.8299   $69.83   $69.85   $69.80  
  Purchase #6 $230.53   10.196%   $254.0348   $254.03   $254.05   $254.00  
  Purchase #7 $205.57   6.144%   $218.2002   $218.20   $218.20   $218.20  
  7 purchase totals = $1,095.43       $1,176.2385   $1,176.23   $1,176.25   $1,176.20