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 $185.26   11.843%   $207.2003   $207.20   $207.20   $207.20  
  Purchase #2 $180.92   11.294%   $201.3531   $201.35   $201.35   $201.40  
  Purchase #3 $101.94   9.574%   $111.6997   $111.70   $111.70   $111.70  
  Purchase #4 $222.43   10.387%   $245.5338   $245.53   $245.55   $245.50  
  Purchase #5 $237.87   3.763%   $246.821   $246.82   $246.80   $246.80  
  Purchase #6 $89.26   4.695%   $93.4508   $93.45   $93.45   $93.50  
  Purchase #7 $37.93   7.210%   $40.6648   $40.66   $40.65   $40.70  
  7 purchase totals = $1,055.61       $1,146.7235   $1,146.71   $1,146.70   $1,146.80