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 $95.48   8.574%   $103.6665   $103.67   $103.65   $103.70  
  Purchase #2 $227.96   5.139%   $239.6749   $239.67   $239.65   $239.70  
  Purchase #3 $242.90   12.447%   $273.1338   $273.13   $273.15   $273.10  
  Purchase #4 $46.78   12.458%   $52.6079   $52.61   $52.60   $52.60  
  Purchase #5 $20.88   9.194%   $22.7997   $22.80   $22.80   $22.80  
  Purchase #6 $122.94   11.169%   $136.6712   $136.67   $136.65   $136.70  
  Purchase #7 $218.95   9.822%   $240.4553   $240.46   $240.45   $240.50  
  7 purchase totals = $975.89       $1,069.0093   $1,069.01   $1,068.95   $1,069.10