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 $188.71   5.609%   $199.2947   $199.29   $199.30   $199.30  
  Purchase #2 $60.78   5.205%   $63.9436   $63.94   $63.95   $63.90  
  Purchase #3 $236.57   4.448%   $247.0926   $247.09   $247.10   $247.10  
  Purchase #4 $185.79   9.557%   $203.546   $203.55   $203.55   $203.50  
  Purchase #5 $195.63   4.133%   $203.7154   $203.72   $203.70   $203.70  
  Purchase #6 $36.34   3.717%   $37.6908   $37.69   $37.70   $37.70  
  Purchase #7 $185.43   4.461%   $193.702   $193.70   $193.70   $193.70  
  7 purchase totals = $1,089.25       $1,148.9851   $1,148.98   $1,149.00   $1,148.90