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 $171.35   13.500%   $194.4823   $194.48   $194.50   $194.50  
  Purchase #2 $163.70   13.686%   $186.104   $186.10   $186.10   $186.10  
  Purchase #3 $29.95   13.221%   $33.9097   $33.91   $33.90   $33.90  
  Purchase #4 $139.32   9.553%   $152.6292   $152.63   $152.65   $152.60  
  Purchase #5 $148.99   6.781%   $159.093   $159.09   $159.10   $159.10  
  Purchase #6 $170.61   13.774%   $194.1098   $194.11   $194.10   $194.10  
  Purchase #7 $181.66   13.119%   $205.492   $205.49   $205.50   $205.50  
  7 purchase totals = $1,005.58       $1,125.8200   $1,125.81   $1,125.85   $1,125.80