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 $112.80   10.818%   $125.0027   $125.00   $125.00   $125.00  
  Purchase #2 $30.40   10.543%   $33.6051   $33.61   $33.60   $33.60  
  Purchase #3 $202.48   7.844%   $218.3625   $218.36   $218.35   $218.40  
  Purchase #4 $187.51   7.314%   $201.2245   $201.22   $201.20   $201.20  
  Purchase #5 $157.30   12.400%   $176.8052   $176.81   $176.80   $176.80  
  Purchase #6 $146.60   3.123%   $151.1783   $151.18   $151.20   $151.20  
  Purchase #7 $169.68   3.781%   $176.0956   $176.10   $176.10   $176.10  
  7 purchase totals = $1,006.77       $1,082.2739   $1,082.28   $1,082.25   $1,082.30