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 $114.82   6.275%   $122.025   $122.03   $122.05   $122.00  
  Purchase #2 $139.52   10.133%   $153.6576   $153.66   $153.65   $153.70  
  Purchase #3 $82.93   5.403%   $87.4107   $87.41   $87.40   $87.40  
  Purchase #4 $205.37   9.543%   $224.9685   $224.97   $224.95   $225.00  
  Purchase #5 $168.56   8.474%   $182.8438   $182.84   $182.85   $182.80  
  Purchase #6 $176.38   9.539%   $193.2049   $193.20   $193.20   $193.20  
  Purchase #7 $163.77   5.119%   $172.1534   $172.15   $172.15   $172.20  
  7 purchase totals = $1,051.35       $1,136.2639   $1,136.26   $1,136.25   $1,136.30