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 $60.34   11.414%   $67.2272   $67.23   $67.25   $67.20  
  Purchase #2 $217.64   7.376%   $233.6931   $233.69   $233.70   $233.70  
  Purchase #3 $135.87   11.122%   $150.9815   $150.98   $151.00   $151.00  
  Purchase #4 $200.76   5.568%   $211.9383   $211.94   $211.95   $211.90  
  Purchase #5 $180.96   13.404%   $205.2159   $205.22   $205.20   $205.20  
  Purchase #6 $43.26   6.751%   $46.1805   $46.18   $46.20   $46.20  
  Purchase #7 $116.57   11.151%   $129.5687   $129.57   $129.55   $129.60  
  7 purchase totals = $955.40       $1,044.8052   $1,044.81   $1,044.85   $1,044.80