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 $151.73   10.691%   $167.9515   $167.95   $167.95   $168.00  
  Purchase #2 $222.86   5.676%   $235.5095   $235.51   $235.50   $235.50  
  Purchase #3 $121.26   11.206%   $134.8484   $134.85   $134.85   $134.80  
  Purchase #4 $218.88   5.696%   $231.3474   $231.35   $231.35   $231.30  
  Purchase #5 $12.33   13.188%   $13.9561   $13.96   $13.95   $14.00  
  Purchase #6 $151.82   10.180%   $167.2753   $167.28   $167.30   $167.30  
  Purchase #7 $193.64   7.473%   $208.1107   $208.11   $208.10   $208.10  
  7 purchase totals = $1,072.52       $1,158.9989   $1,159.01   $1,159.00   $1,159.00