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 $176.50   3.413%   $182.5239   $182.52   $182.50   $182.50  
  Purchase #2 $240.93   10.657%   $266.6059   $266.61   $266.60   $266.60  
  Purchase #3 $32.32   4.584%   $33.8015   $33.80   $33.80   $33.80  
  Purchase #4 $76.71   10.515%   $84.7761   $84.78   $84.80   $84.80  
  Purchase #5 $131.34   4.320%   $137.0139   $137.01   $137.00   $137.00  
  Purchase #6 $143.90   6.750%   $153.6133   $153.61   $153.60   $153.60  
  Purchase #7 $194.54   3.187%   $200.74   $200.74   $200.75   $200.70  
  7 purchase totals = $996.24       $1,059.0746   $1,059.07   $1,059.05   $1,059.00