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 $208.88   11.413%   $232.7195   $232.72   $232.70   $232.70  
  Purchase #2 $57.59   7.362%   $61.8298   $61.83   $61.85   $61.80  
  Purchase #3 $65.79   5.297%   $69.2749   $69.27   $69.25   $69.30  
  Purchase #4 $148.84   5.346%   $156.797   $156.80   $156.80   $156.80  
  Purchase #5 $35.69   7.455%   $38.3507   $38.35   $38.35   $38.40  
  Purchase #6 $196.96   7.369%   $211.474   $211.47   $211.45   $211.50  
  Purchase #7 $224.61   9.586%   $246.1411   $246.14   $246.15   $246.10  
  7 purchase totals = $938.36       $1,016.5870   $1,016.58   $1,016.55   $1,016.60