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 $34.25   4.191%   $35.6854   $35.69   $35.70   $35.70  
  Purchase #2 $210.93   7.353%   $226.4397   $226.44   $226.45   $226.40  
  Purchase #3 $166.55   11.417%   $185.565   $185.57   $185.55   $185.60  
  Purchase #4 $194.48   13.316%   $220.377   $220.38   $220.40   $220.40  
  Purchase #5 $199.34   6.170%   $211.6393   $211.64   $211.65   $211.60  
  Purchase #6 $194.93   9.854%   $214.1384   $214.14   $214.15   $214.10  
  Purchase #7 $14.73   12.789%   $16.6138   $16.61   $16.60   $16.60  
  7 purchase totals = $1,015.21       $1,110.4586   $1,110.47   $1,110.50   $1,110.40