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 $23.67   5.871%   $25.0597   $25.06   $25.05   $25.10  
  Purchase #2 $182.84   6.110%   $194.0115   $194.01   $194.00   $194.00  
  Purchase #3 $71.61   5.618%   $75.633   $75.63   $75.65   $75.60  
  Purchase #4 $176.25   8.670%   $191.5309   $191.53   $191.55   $191.50  
  Purchase #5 $134.77   13.565%   $153.0516   $153.05   $153.05   $153.10  
  Purchase #6 $175.83   13.742%   $199.9926   $199.99   $200.00   $200.00  
  Purchase #7 $34.64   4.812%   $36.3069   $36.31   $36.30   $36.30  
  7 purchase totals = $799.61       $875.5862   $875.58   $875.60   $875.60