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 $212.51   11.648%   $237.2632   $237.26   $237.25   $237.30  
  Purchase #2 $78.92   4.701%   $82.63   $82.63   $82.65   $82.60  
  Purchase #3 $249.45   10.460%   $275.5425   $275.54   $275.55   $275.50  
  Purchase #4 $153.63   5.324%   $161.8093   $161.81   $161.80   $161.80  
  Purchase #5 $37.29   10.873%   $41.3445   $41.34   $41.35   $41.30  
  Purchase #6 $109.66   4.644%   $114.7526   $114.75   $114.75   $114.80  
  Purchase #7 $108.77   12.739%   $122.6262   $122.63   $122.65   $122.60  
  7 purchase totals = $950.23       $1,035.9683   $1,035.96   $1,036.00   $1,035.90