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 $181.58   5.660%   $191.8574   $191.86   $191.85   $191.90  
  Purchase #2 $236.90   7.114%   $253.7531   $253.75   $253.75   $253.80  
  Purchase #3 $216.63   11.422%   $241.3735   $241.37   $241.35   $241.40  
  Purchase #4 $23.91   11.448%   $26.6472   $26.65   $26.65   $26.60  
  Purchase #5 $225.87   11.207%   $251.1833   $251.18   $251.20   $251.20  
  Purchase #6 $141.65   8.828%   $154.1549   $154.15   $154.15   $154.20  
  Purchase #7 $59.53   10.252%   $65.633   $65.63   $65.65   $65.60  
  7 purchase totals = $1,086.07       $1,184.6024   $1,184.59   $1,184.60   $1,184.70