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 $62.86   9.501%   $68.8323   $68.83   $68.85   $68.80  
  Purchase #2 $47.32   4.104%   $49.262   $49.26   $49.25   $49.30  
  Purchase #3 $134.87   10.684%   $149.2795   $149.28   $149.30   $149.30  
  Purchase #4 $166.42   11.835%   $186.1158   $186.12   $186.10   $186.10  
  Purchase #5 $166.27   3.272%   $171.7104   $171.71   $171.70   $171.70  
  Purchase #6 $232.70   13.347%   $263.7585   $263.76   $263.75   $263.80  
  Purchase #7 $135.48   5.587%   $143.0493   $143.05   $143.05   $143.00  
  7 purchase totals = $945.92       $1,032.0078   $1,032.01   $1,032.00   $1,032.00