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 $187.62   3.134%   $193.5   $193.50   $193.50   $193.50  
  Purchase #2 $43.80   11.645%   $48.9005   $48.90   $48.90   $48.90  
  Purchase #3 $157.34   12.808%   $177.4921   $177.49   $177.50   $177.50  
  Purchase #4 $228.37   12.657%   $257.2748   $257.27   $257.25   $257.30  
  Purchase #5 $40.65   13.607%   $46.1812   $46.18   $46.20   $46.20  
  Purchase #6 $212.84   11.220%   $236.7206   $236.72   $236.70   $236.70  
  Purchase #7 $95.48   6.228%   $101.4265   $101.43   $101.45   $101.40  
  7 purchase totals = $966.10       $1,061.4957   $1,061.49   $1,061.50   $1,061.50