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 $60.96   4.346%   $63.6093   $63.61   $63.60   $63.60  
  Purchase #2 $163.62   12.676%   $184.3605   $184.36   $184.35   $184.40  
  Purchase #3 $196.31   6.600%   $209.2665   $209.27   $209.25   $209.30  
  Purchase #4 $231.56   3.290%   $239.1783   $239.18   $239.20   $239.20  
  Purchase #5 $241.45   11.416%   $269.0139   $269.01   $269.00   $269.00  
  Purchase #6 $56.54   12.861%   $63.8116   $63.81   $63.80   $63.80  
  Purchase #7 $185.65   4.735%   $194.4405   $194.44   $194.45   $194.40  
  7 purchase totals = $1,136.09       $1,223.6806   $1,223.68   $1,223.65   $1,223.70