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 $192.44   4.458%   $201.019   $201.02   $201.00   $201.00  
  Purchase #2 $43.46   3.672%   $45.0559   $45.06   $45.05   $45.10  
  Purchase #3 $182.43   9.827%   $200.3574   $200.36   $200.35   $200.40  
  Purchase #4 $151.26   4.640%   $158.2785   $158.28   $158.30   $158.30  
  Purchase #5 $18.49   12.146%   $20.7358   $20.74   $20.75   $20.70  
  Purchase #6 $51.50   10.617%   $56.9678   $56.97   $56.95   $57.00  
  Purchase #7 $174.68   6.276%   $185.6429   $185.64   $185.65   $185.60  
  7 purchase totals = $814.26       $868.0573   $868.07   $868.05   $868.10