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 $246.50   6.517%   $262.5644   $262.56   $262.55   $262.60  
  Purchase #2 $93.52   9.120%   $102.049   $102.05   $102.05   $102.00  
  Purchase #3 $134.73   13.744%   $153.2473   $153.25   $153.25   $153.20  
  Purchase #4 $173.61   11.415%   $193.4276   $193.43   $193.45   $193.40  
  Purchase #5 $24.67   5.811%   $26.1036   $26.10   $26.10   $26.10  
  Purchase #6 $243.88   10.330%   $269.0728   $269.07   $269.05   $269.10  
  Purchase #7 $204.81   3.297%   $211.5626   $211.56   $211.55   $211.60  
  7 purchase totals = $1,121.72       $1,218.0273   $1,218.02   $1,218.00   $1,218.00