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 $76.85   9.383%   $84.0608   $84.06   $84.05   $84.10  
  Purchase #2 $203.97   5.343%   $214.8681   $214.87   $214.85   $214.90  
  Purchase #3 $195.78   12.250%   $219.7631   $219.76   $219.75   $219.80  
  Purchase #4 $56.31   9.394%   $61.5998   $61.60   $61.60   $61.60  
  Purchase #5 $206.45   13.261%   $233.8273   $233.83   $233.85   $233.80  
  Purchase #6 $204.72   8.644%   $222.416   $222.42   $222.40   $222.40  
  Purchase #7 $70.91   8.424%   $76.8835   $76.88   $76.90   $76.90  
  7 purchase totals = $1,014.99       $1,113.4186   $1,113.42   $1,113.40   $1,113.50