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 $237.52   10.643%   $262.7993   $262.80   $262.80   $262.80  
  Purchase #2 $38.51   7.409%   $41.3632   $41.36   $41.35   $41.40  
  Purchase #3 $113.89   13.632%   $129.4155   $129.42   $129.40   $129.40  
  Purchase #4 $172.53   6.484%   $183.7168   $183.72   $183.70   $183.70  
  Purchase #5 $69.94   9.872%   $76.8445   $76.84   $76.85   $76.80  
  Purchase #6 $174.70   9.488%   $191.2755   $191.28   $191.30   $191.30  
  Purchase #7 $220.66   9.583%   $241.8058   $241.81   $241.80   $241.80  
  7 purchase totals = $1,027.75       $1,127.2206   $1,127.23   $1,127.20   $1,127.20