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 $64.36   6.789%   $68.7294   $68.73   $68.75   $68.70  
  Purchase #2 $211.57   5.374%   $222.9398   $222.94   $222.95   $222.90  
  Purchase #3 $60.48   8.275%   $65.4847   $65.48   $65.50   $65.50  
  Purchase #4 $216.46   4.200%   $225.5513   $225.55   $225.55   $225.60  
  Purchase #5 $211.28   4.773%   $221.3644   $221.36   $221.35   $221.40  
  Purchase #6 $239.84   9.471%   $262.5552   $262.56   $262.55   $262.60  
  Purchase #7 $97.77   7.677%   $105.2758   $105.28   $105.30   $105.30  
  7 purchase totals = $1,101.76       $1,171.9006   $1,171.90   $1,171.95   $1,172.00