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 $198.99   8.524%   $215.9519   $215.95   $215.95   $216.00  
  Purchase #2 $230.35   3.575%   $238.585   $238.59   $238.60   $238.60  
  Purchase #3 $13.95   4.543%   $14.5837   $14.58   $14.60   $14.60  
  Purchase #4 $38.51   11.205%   $42.825   $42.83   $42.85   $42.80  
  Purchase #5 $169.32   4.326%   $176.6448   $176.64   $176.65   $176.60  
  Purchase #6 $156.68   11.769%   $175.1197   $175.12   $175.10   $175.10  
  Purchase #7 $76.32   10.843%   $84.5954   $84.60   $84.60   $84.60  
  7 purchase totals = $884.12       $948.3055   $948.31   $948.35   $948.30