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 $44.89   4.796%   $47.0429   $47.04   $47.05   $47.00  
  Purchase #2 $205.48   3.552%   $212.7786   $212.78   $212.80   $212.80  
  Purchase #3 $101.88   5.482%   $107.4651   $107.47   $107.45   $107.50  
  Purchase #4 $76.29   13.621%   $86.6815   $86.68   $86.70   $86.70  
  Purchase #5 $144.28   7.807%   $155.5439   $155.54   $155.55   $155.50  
  Purchase #6 $96.30   9.155%   $105.1163   $105.12   $105.10   $105.10  
  Purchase #7 $25.91   11.202%   $28.8124   $28.81   $28.80   $28.80  
  7 purchase totals = $695.03       $743.4407   $743.44   $743.45   $743.40