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 $55.54   11.683%   $62.0287   $62.03   $62.05   $62.00  
  Purchase #2 $149.99   8.668%   $162.9911   $162.99   $163.00   $163.00  
  Purchase #3 $30.78   4.643%   $32.2091   $32.21   $32.20   $32.20  
  Purchase #4 $174.54   6.551%   $185.9741   $185.97   $185.95   $186.00  
  Purchase #5 $38.33   8.409%   $41.5532   $41.55   $41.55   $41.60  
  Purchase #6 $56.89   11.166%   $63.2423   $63.24   $63.25   $63.20  
  Purchase #7 $198.95   6.115%   $211.1158   $211.12   $211.10   $211.10  
  7 purchase totals = $705.02       $759.1143   $759.11   $759.10   $759.10