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 $193.44   4.860%   $202.8412   $202.84   $202.85   $202.80  
  Purchase #2 $209.67   6.221%   $222.7136   $222.71   $222.70   $222.70  
  Purchase #3 $92.45   11.749%   $103.312   $103.31   $103.30   $103.30  
  Purchase #4 $55.66   4.649%   $58.2476   $58.25   $58.25   $58.20  
  Purchase #5 $177.62   13.175%   $201.0214   $201.02   $201.00   $201.00  
  Purchase #6 $144.34   13.495%   $163.8187   $163.82   $163.80   $163.80  
  Purchase #7 $202.78   6.275%   $215.5044   $215.50   $215.50   $215.50  
  7 purchase totals = $1,075.96       $1,167.4589   $1,167.45   $1,167.40   $1,167.30