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 $195.48   4.668%   $204.605   $204.61   $204.60   $204.60  
  Purchase #2 $51.67   12.824%   $58.2962   $58.30   $58.30   $58.30  
  Purchase #3 $161.36   10.470%   $178.2544   $178.25   $178.25   $178.30  
  Purchase #4 $69.58   3.350%   $71.9109   $71.91   $71.90   $71.90  
  Purchase #5 $127.71   9.774%   $140.1924   $140.19   $140.20   $140.20  
  Purchase #6 $190.89   9.499%   $209.0226   $209.02   $209.00   $209.00  
  Purchase #7 $96.93   10.791%   $107.3897   $107.39   $107.40   $107.40  
  7 purchase totals = $893.62       $969.6712   $969.67   $969.65   $969.70