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 $188.77   3.287%   $194.9749   $194.97   $194.95   $195.00  
  Purchase #2 $148.63   11.761%   $166.1104   $166.11   $166.10   $166.10  
  Purchase #3 $10.29   12.212%   $11.5466   $11.55   $11.55   $11.50  
  Purchase #4 $47.83   7.202%   $51.2747   $51.27   $51.25   $51.30  
  Purchase #5 $219.49   3.838%   $227.914   $227.91   $227.90   $227.90  
  Purchase #6 $198.67   13.156%   $224.807   $224.81   $224.80   $224.80  
  Purchase #7 $239.64   12.371%   $269.2859   $269.29   $269.30   $269.30  
  7 purchase totals = $1,053.32       $1,145.9135   $1,145.91   $1,145.85   $1,145.90