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 $214.66   8.853%   $233.6638   $233.66   $233.65   $233.70  
  Purchase #2 $227.94   11.807%   $254.8529   $254.85   $254.85   $254.90  
  Purchase #3 $233.37   10.363%   $257.5541   $257.55   $257.55   $257.60  
  Purchase #4 $218.26   10.598%   $241.3912   $241.39   $241.40   $241.40  
  Purchase #5 $200.86   7.496%   $215.9165   $215.92   $215.90   $215.90  
  Purchase #6 $210.58   10.215%   $232.0907   $232.09   $232.10   $232.10  
  Purchase #7 $180.44   6.252%   $191.7211   $191.72   $191.70   $191.70  
  7 purchase totals = $1,486.11       $1,627.1903   $1,627.18   $1,627.15   $1,627.30