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 $84.94   12.408%   $95.4794   $95.48   $95.50   $95.50  
  Purchase #2 $60.97   6.520%   $64.9452   $64.95   $64.95   $64.90  
  Purchase #3 $133.35   6.523%   $142.0484   $142.05   $142.05   $142.00  
  Purchase #4 $115.80   3.799%   $120.1992   $120.20   $120.20   $120.20  
  Purchase #5 $165.91   4.729%   $173.7559   $173.76   $173.75   $173.80  
  Purchase #6 $114.25   3.109%   $117.802   $117.80   $117.80   $117.80  
  Purchase #7 $181.99   12.560%   $204.8479   $204.85   $204.85   $204.80  
  7 purchase totals = $857.21       $919.0780   $919.09   $919.10   $919.00