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 $158.49   11.258%   $176.3328   $176.33   $176.35   $176.30  
  Purchase #2 $182.44   10.354%   $201.3298   $201.33   $201.35   $201.30  
  Purchase #3 $117.52   10.662%   $130.05   $130.05   $130.05   $130.10  
  Purchase #4 $131.29   3.380%   $135.7276   $135.73   $135.75   $135.70  
  Purchase #5 $190.96   6.469%   $203.3132   $203.31   $203.30   $203.30  
  Purchase #6 $154.71   8.574%   $167.9748   $167.97   $167.95   $168.00  
  Purchase #7 $161.28   13.231%   $182.619   $182.62   $182.60   $182.60  
  7 purchase totals = $1,096.69       $1,197.3472   $1,197.34   $1,197.35   $1,197.30