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 $194.68   3.251%   $201.009   $201.01   $201.00   $201.00  
  Purchase #2 $13.42   9.844%   $14.7411   $14.74   $14.75   $14.70  
  Purchase #3 $188.34   5.676%   $199.0302   $199.03   $199.05   $199.00  
  Purchase #4 $216.55   4.853%   $227.0592   $227.06   $227.05   $227.10  
  Purchase #5 $190.33   9.580%   $208.5636   $208.56   $208.55   $208.60  
  Purchase #6 $243.80   5.406%   $256.9798   $256.98   $257.00   $257.00  
  Purchase #7 $40.79   10.523%   $45.0823   $45.08   $45.10   $45.10  
  7 purchase totals = $1,087.91       $1,152.4652   $1,152.46   $1,152.50   $1,152.50