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 $158.71   10.247%   $174.973   $174.97   $174.95   $175.00  
  Purchase #2 $233.61   12.395%   $262.566   $262.57   $262.55   $262.60  
  Purchase #3 $135.74   12.591%   $152.831   $152.83   $152.85   $152.80  
  Purchase #4 $228.33   12.601%   $257.1019   $257.10   $257.10   $257.10  
  Purchase #5 $101.86   6.368%   $108.3464   $108.35   $108.35   $108.30  
  Purchase #6 $63.46   13.281%   $71.8881   $71.89   $71.90   $71.90  
  Purchase #7 $46.35   10.246%   $51.099   $51.10   $51.10   $51.10  
  7 purchase totals = $968.06       $1,078.8054   $1,078.81   $1,078.80   $1,078.80