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 $208.31   12.856%   $235.0903   $235.09   $235.10   $235.10  
  Purchase #2 $27.79   5.628%   $29.354   $29.35   $29.35   $29.40  
  Purchase #3 $46.47   11.665%   $51.8907   $51.89   $51.90   $51.90  
  Purchase #4 $45.30   3.442%   $46.8592   $46.86   $46.85   $46.90  
  Purchase #5 $197.26   12.439%   $221.7972   $221.80   $221.80   $221.80  
  Purchase #6 $245.84   9.581%   $269.3939   $269.39   $269.40   $269.40  
  Purchase #7 $104.68   7.482%   $112.5122   $112.51   $112.50   $112.50  
  7 purchase totals = $875.65       $966.8975   $966.89   $966.90   $967.00