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 $69.25   10.459%   $76.4929   $76.49   $76.50   $76.50  
  Purchase #2 $155.36   6.652%   $165.6945   $165.69   $165.70   $165.70  
  Purchase #3 $158.60   4.714%   $166.0764   $166.08   $166.10   $166.10  
  Purchase #4 $203.41   11.175%   $226.1411   $226.14   $226.15   $226.10  
  Purchase #5 $100.73   7.119%   $107.901   $107.90   $107.90   $107.90  
  Purchase #6 $20.70   7.869%   $22.3289   $22.33   $22.35   $22.30  
  Purchase #7 $196.71   7.799%   $212.0514   $212.05   $212.05   $212.10  
  7 purchase totals = $904.76       $976.6862   $976.68   $976.75   $976.70