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 $67.25   10.867%   $74.5581   $74.56   $74.55   $74.60  
  Purchase #2 $9.97   10.371%   $11.004   $11.00   $11.00   $11.00  
  Purchase #3 $12.74   10.567%   $14.0862   $14.09   $14.10   $14.10  
  Purchase #4 $141.53   8.841%   $154.0427   $154.04   $154.05   $154.00  
  Purchase #5 $195.83   9.663%   $214.7531   $214.75   $214.75   $214.80  
  Purchase #6 $247.45   11.497%   $275.8993   $275.90   $275.90   $275.90  
  Purchase #7 $171.66   5.498%   $181.0979   $181.10   $181.10   $181.10  
  7 purchase totals = $846.43       $925.4413   $925.44   $925.45   $925.50