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 $163.75   11.292%   $182.2407   $182.24   $182.25   $182.20  
  Purchase #2 $168.79   5.368%   $177.8506   $177.85   $177.85   $177.90  
  Purchase #3 $245.80   13.135%   $278.0858   $278.09   $278.10   $278.10  
  Purchase #4 $22.77   5.456%   $24.0123   $24.01   $24.00   $24.00  
  Purchase #5 $193.88   6.533%   $206.5462   $206.55   $206.55   $206.50  
  Purchase #6 $104.57   5.746%   $110.5786   $110.58   $110.60   $110.60  
  Purchase #7 $76.72   6.745%   $81.8948   $81.89   $81.90   $81.90  
  7 purchase totals = $976.28       $1,061.2090   $1,061.21   $1,061.25   $1,061.20