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 $96.30   5.604%   $101.6967   $101.70   $101.70   $101.70  
  Purchase #2 $245.72   13.204%   $278.1649   $278.16   $278.15   $278.20  
  Purchase #3 $199.27   13.374%   $225.9204   $225.92   $225.90   $225.90  
  Purchase #4 $153.78   7.646%   $165.538   $165.54   $165.55   $165.50  
  Purchase #5 $76.25   9.714%   $83.6569   $83.66   $83.65   $83.70  
  Purchase #6 $212.41   6.657%   $226.5501   $226.55   $226.55   $226.60  
  Purchase #7 $49.81   5.451%   $52.5251   $52.53   $52.55   $52.50  
  7 purchase totals = $1,033.54       $1,134.0521   $1,134.06   $1,134.05   $1,134.10