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 $44.81   3.242%   $46.2627   $46.26   $46.25   $46.30  
  Purchase #2 $235.33   8.350%   $254.9801   $254.98   $255.00   $255.00  
  Purchase #3 $158.96   11.446%   $177.1546   $177.15   $177.15   $177.20  
  Purchase #4 $198.47   12.241%   $222.7647   $222.76   $222.75   $222.80  
  Purchase #5 $148.79   4.447%   $155.4067   $155.41   $155.40   $155.40  
  Purchase #6 $231.57   4.155%   $241.1917   $241.19   $241.20   $241.20  
  Purchase #7 $101.93   8.214%   $110.3025   $110.30   $110.30   $110.30  
  7 purchase totals = $1,119.86       $1,208.0630   $1,208.05   $1,208.05   $1,208.20