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 $169.61   10.460%   $187.3512   $187.35   $187.35   $187.40  
  Purchase #2 $195.70   6.104%   $207.6455   $207.65   $207.65   $207.60  
  Purchase #3 $215.91   4.584%   $225.8073   $225.81   $225.80   $225.80  
  Purchase #4 $157.58   3.569%   $163.204   $163.20   $163.20   $163.20  
  Purchase #5 $225.63   7.712%   $243.0306   $243.03   $243.05   $243.00  
  Purchase #6 $95.54   12.393%   $107.3803   $107.38   $107.40   $107.40  
  Purchase #7 $187.95   8.611%   $204.1344   $204.13   $204.15   $204.10  
  7 purchase totals = $1,247.92       $1,338.5533   $1,338.55   $1,338.60   $1,338.50