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 $214.67   10.486%   $237.1803   $237.18   $237.20   $237.20  
  Purchase #2 $111.83   12.460%   $125.764   $125.76   $125.75   $125.80  
  Purchase #3 $58.85   11.458%   $65.593   $65.59   $65.60   $65.60  
  Purchase #4 $206.49   6.302%   $219.503   $219.50   $219.50   $219.50  
  Purchase #5 $199.69   11.386%   $222.4267   $222.43   $222.45   $222.40  
  Purchase #6 $248.96   8.437%   $269.9648   $269.96   $269.95   $270.00  
  Purchase #7 $50.65   6.106%   $53.7427   $53.74   $53.75   $53.70  
  7 purchase totals = $1,091.14       $1,194.1745   $1,194.16   $1,194.20   $1,194.20