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 $55.68   11.459%   $62.0604   $62.06   $62.05   $62.10  
  Purchase #2 $34.66   5.192%   $36.4595   $36.46   $36.45   $36.50  
  Purchase #3 $32.93   6.259%   $34.9911   $34.99   $35.00   $35.00  
  Purchase #4 $92.51   10.157%   $101.9062   $101.91   $101.90   $101.90  
  Purchase #5 $22.58   8.104%   $24.4099   $24.41   $24.40   $24.40  
  Purchase #6 $161.86   6.247%   $171.9714   $171.97   $171.95   $172.00  
  Purchase #7 $89.66   4.389%   $93.5952   $93.60   $93.60   $93.60  
  7 purchase totals = $489.88       $525.3937   $525.40   $525.35   $525.50