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 $168.34   3.372%   $174.0164   $174.02   $174.00   $174.00  
  Purchase #2 $57.93   13.584%   $65.7992   $65.80   $65.80   $65.80  
  Purchase #3 $56.69   13.334%   $64.249   $64.25   $64.25   $64.20  
  Purchase #4 $163.64   8.792%   $178.0272   $178.03   $178.05   $178.00  
  Purchase #5 $132.67   5.144%   $139.4945   $139.49   $139.50   $139.50  
  Purchase #6 $210.30   12.162%   $235.8767   $235.88   $235.90   $235.90  
  Purchase #7 $170.55   3.547%   $176.5994   $176.60   $176.60   $176.60  
  7 purchase totals = $960.12       $1,034.0624   $1,034.07   $1,034.10   $1,034.00