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 $248.29   5.538%   $262.0403   $262.04   $262.05   $262.00  
  Purchase #2 $34.45   6.626%   $36.7327   $36.73   $36.75   $36.70  
  Purchase #3 $169.46   9.769%   $186.0145   $186.01   $186.00   $186.00  
  Purchase #4 $222.48   10.697%   $246.2787   $246.28   $246.30   $246.30  
  Purchase #5 $151.34   5.427%   $159.5532   $159.55   $159.55   $159.60  
  Purchase #6 $124.55   12.851%   $140.5559   $140.56   $140.55   $140.60  
  Purchase #7 $144.83   5.648%   $153.01   $153.01   $153.00   $153.00  
  7 purchase totals = $1,095.40       $1,184.1853   $1,184.18   $1,184.20   $1,184.20