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 $92.84   5.403%   $97.8561   $97.86   $97.85   $97.90  
  Purchase #2 $219.91   5.274%   $231.5081   $231.51   $231.50   $231.50  
  Purchase #3 $186.79   3.169%   $192.7094   $192.71   $192.70   $192.70  
  Purchase #4 $142.99   13.396%   $162.1449   $162.14   $162.15   $162.10  
  Purchase #5 $44.57   4.699%   $46.6643   $46.66   $46.65   $46.70  
  Purchase #6 $42.73   11.396%   $47.5995   $47.60   $47.60   $47.60  
  Purchase #7 $245.46   3.483%   $254.0094   $254.01   $254.00   $254.00  
  7 purchase totals = $975.29       $1,032.4917   $1,032.49   $1,032.45   $1,032.50