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 $97.26   11.239%   $108.1911   $108.19   $108.20   $108.20  
  Purchase #2 $183.26   5.751%   $193.7993   $193.80   $193.80   $193.80  
  Purchase #3 $11.99   6.761%   $12.8006   $12.80   $12.80   $12.80  
  Purchase #4 $244.61   6.170%   $259.7024   $259.70   $259.70   $259.70  
  Purchase #5 $83.58   3.581%   $86.573   $86.57   $86.55   $86.60  
  Purchase #6 $219.52   9.601%   $240.5961   $240.60   $240.60   $240.60  
  Purchase #7 $15.92   4.548%   $16.644   $16.64   $16.65   $16.60  
  7 purchase totals = $856.14       $918.3065   $918.30   $918.30   $918.30