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 $124.53   13.779%   $141.689   $141.69   $141.70   $141.70  
  Purchase #2 $187.97   10.604%   $207.9023   $207.90   $207.90   $207.90  
  Purchase #3 $39.95   4.839%   $41.8832   $41.88   $41.90   $41.90  
  Purchase #4 $145.30   9.689%   $159.3781   $159.38   $159.40   $159.40  
  Purchase #5 $228.68   5.507%   $241.2734   $241.27   $241.25   $241.30  
  Purchase #6 $241.41   12.710%   $272.0932   $272.09   $272.10   $272.10  
  Purchase #7 $64.51   6.146%   $68.4748   $68.47   $68.45   $68.50  
  7 purchase totals = $1,032.35       $1,132.6940   $1,132.68   $1,132.70   $1,132.80