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 $46.50   13.645%   $52.8449   $52.84   $52.85   $52.80  
  Purchase #2 $82.76   4.577%   $86.5479   $86.55   $86.55   $86.50  
  Purchase #3 $114.36   8.410%   $123.9777   $123.98   $124.00   $124.00  
  Purchase #4 $167.47   8.233%   $181.2578   $181.26   $181.25   $181.30  
  Purchase #5 $219.29   9.419%   $239.9449   $239.94   $239.95   $239.90  
  Purchase #6 $179.98   7.394%   $193.2877   $193.29   $193.30   $193.30  
  Purchase #7 $147.71   4.838%   $154.8562   $154.86   $154.85   $154.90  
  7 purchase totals = $958.07       $1,032.7171   $1,032.72   $1,032.75   $1,032.70