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 $214.58   5.467%   $226.3111   $226.31   $226.30   $226.30  
  Purchase #2 $153.89   6.538%   $163.9513   $163.95   $163.95   $164.00  
  Purchase #3 $192.67   6.189%   $204.5943   $204.59   $204.60   $204.60  
  Purchase #4 $245.62   5.149%   $258.267   $258.27   $258.25   $258.30  
  Purchase #5 $167.39   10.412%   $184.8186   $184.82   $184.80   $184.80  
  Purchase #6 $202.89   12.734%   $228.726   $228.73   $228.75   $228.70  
  Purchase #7 $6.95   6.172%   $7.379   $7.38   $7.40   $7.40  
  7 purchase totals = $1,183.99       $1,274.0473   $1,274.05   $1,274.05   $1,274.10