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 $57.92   6.502%   $61.686   $61.69   $61.70   $61.70  
  Purchase #2 $214.27   7.603%   $230.5609   $230.56   $230.55   $230.60  
  Purchase #3 $177.27   9.735%   $194.5272   $194.53   $194.55   $194.50  
  Purchase #4 $148.26   10.415%   $163.7013   $163.70   $163.70   $163.70  
  Purchase #5 $227.43   6.268%   $241.6853   $241.69   $241.70   $241.70  
  Purchase #6 $185.67   10.639%   $205.4234   $205.42   $205.40   $205.40  
  Purchase #7 $73.32   7.506%   $78.8234   $78.82   $78.80   $78.80  
  7 purchase totals = $1,084.14       $1,176.4075   $1,176.41   $1,176.40   $1,176.40