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 $154.79   8.289%   $167.6205   $167.62   $167.60   $167.60  
  Purchase #2 $214.38   8.832%   $233.314   $233.31   $233.30   $233.30  
  Purchase #3 $22.57   10.395%   $24.9162   $24.92   $24.90   $24.90  
  Purchase #4 $224.58   3.854%   $233.2353   $233.24   $233.25   $233.20  
  Purchase #5 $158.85   9.172%   $173.4197   $173.42   $173.40   $173.40  
  Purchase #6 $175.52   7.574%   $188.8139   $188.81   $188.80   $188.80  
  Purchase #7 $152.56   5.555%   $161.0347   $161.03   $161.05   $161.00  
  7 purchase totals = $1,103.25       $1,182.3543   $1,182.35   $1,182.30   $1,182.20