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 $163.98   11.463%   $182.777   $182.78   $182.80   $182.80  
  Purchase #2 $225.94   5.202%   $237.6934   $237.69   $237.70   $237.70  
  Purchase #3 $98.83   3.170%   $101.9629   $101.96   $101.95   $102.00  
  Purchase #4 $161.90   6.651%   $172.668   $172.67   $172.65   $172.70  
  Purchase #5 $181.93   4.340%   $189.8258   $189.83   $189.85   $189.80  
  Purchase #6 $21.55   10.167%   $23.741   $23.74   $23.75   $23.70  
  Purchase #7 $142.89   12.186%   $160.3026   $160.30   $160.30   $160.30  
  7 purchase totals = $997.02       $1,068.9707   $1,068.97   $1,069.00   $1,069.00