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 $65.54   5.206%   $68.952   $68.95   $68.95   $69.00  
  Purchase #2 $56.97   5.462%   $60.0817   $60.08   $60.10   $60.10  
  Purchase #3 $69.54   3.255%   $71.8035   $71.80   $71.80   $71.80  
  Purchase #4 $33.34   6.112%   $35.3777   $35.38   $35.40   $35.40  
  Purchase #5 $175.38   9.146%   $191.4203   $191.42   $191.40   $191.40  
  Purchase #6 $246.61   10.736%   $273.086   $273.09   $273.10   $273.10  
  Purchase #7 $103.93   7.483%   $111.7071   $111.71   $111.70   $111.70  
  7 purchase totals = $751.31       $812.4283   $812.43   $812.45   $812.50