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 $86.56   13.236%   $98.0171   $98.02   $98.00   $98.00  
  Purchase #2 $41.75   9.590%   $45.7538   $45.75   $45.75   $45.80  
  Purchase #3 $107.57   5.457%   $113.4401   $113.44   $113.45   $113.40  
  Purchase #4 $240.61   13.469%   $273.0178   $273.02   $273.00   $273.00  
  Purchase #5 $33.65   6.499%   $35.8369   $35.84   $35.85   $35.80  
  Purchase #6 $35.85   8.826%   $39.0141   $39.01   $39.00   $39.00  
  Purchase #7 $84.66   13.383%   $95.99   $95.99   $96.00   $96.00  
  7 purchase totals = $630.65       $701.0698   $701.07   $701.05   $701.00