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 $196.60   5.767%   $207.9379   $207.94   $207.95   $207.90  
  Purchase #2 $85.69   9.755%   $94.0491   $94.05   $94.05   $94.00  
  Purchase #3 $12.82   7.231%   $13.747   $13.75   $13.75   $13.70  
  Purchase #4 $118.41   11.643%   $132.1965   $132.20   $132.20   $132.20  
  Purchase #5 $90.42   4.616%   $94.5938   $94.59   $94.60   $94.60  
  Purchase #6 $159.59   12.223%   $179.0967   $179.10   $179.10   $179.10  
  Purchase #7 $192.27   10.188%   $211.8585   $211.86   $211.85   $211.90  
  7 purchase totals = $855.80       $933.4795   $933.49   $933.50   $933.40