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 $37.41   9.610%   $41.0051   $41.01   $41.00   $41.00  
  Purchase #2 $236.29   4.303%   $246.4576   $246.46   $246.45   $246.50  
  Purchase #3 $15.35   8.175%   $16.6049   $16.60   $16.60   $16.60  
  Purchase #4 $91.37   4.801%   $95.7567   $95.76   $95.75   $95.80  
  Purchase #5 $249.36   4.184%   $259.7932   $259.79   $259.80   $259.80  
  Purchase #6 $222.85   11.611%   $248.7251   $248.73   $248.75   $248.70  
  Purchase #7 $169.53   3.749%   $175.8857   $175.89   $175.90   $175.90  
  7 purchase totals = $1,022.16       $1,084.2283   $1,084.24   $1,084.25   $1,084.30