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 $185.57   8.407%   $201.1709   $201.17   $201.15   $201.20  
  Purchase #2 $68.56   9.382%   $74.9923   $74.99   $75.00   $75.00  
  Purchase #3 $56.84   5.465%   $59.9463   $59.95   $59.95   $59.90  
  Purchase #4 $233.71   12.662%   $263.3024   $263.30   $263.30   $263.30  
  Purchase #5 $93.66   4.569%   $97.9393   $97.94   $97.95   $97.90  
  Purchase #6 $151.53   6.556%   $161.4643   $161.46   $161.45   $161.50  
  Purchase #7 $219.25   3.161%   $226.1805   $226.18   $226.20   $226.20  
  7 purchase totals = $1,009.12       $1,084.9960   $1,084.99   $1,085.00   $1,085.00