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 $62.80   3.251%   $64.8416   $64.84   $64.85   $64.80  
  Purchase #2 $242.45   9.521%   $265.5337   $265.53   $265.55   $265.50  
  Purchase #3 $111.80   4.759%   $117.1206   $117.12   $117.10   $117.10  
  Purchase #4 $86.68   3.103%   $89.3697   $89.37   $89.35   $89.40  
  Purchase #5 $66.75   11.482%   $74.4142   $74.41   $74.40   $74.40  
  Purchase #6 $248.73   8.146%   $268.9915   $268.99   $269.00   $269.00  
  Purchase #7 $176.50   6.303%   $187.6248   $187.62   $187.60   $187.60  
  7 purchase totals = $995.71       $1,067.8961   $1,067.88   $1,067.85   $1,067.80