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 $135.87   8.640%   $147.6092   $147.61   $147.60   $147.60  
  Purchase #2 $24.70   4.304%   $25.7631   $25.76   $25.75   $25.80  
  Purchase #3 $210.25   13.758%   $239.1762   $239.18   $239.20   $239.20  
  Purchase #4 $216.58   11.167%   $240.7655   $240.77   $240.75   $240.80  
  Purchase #5 $45.94   10.119%   $50.5887   $50.59   $50.60   $50.60  
  Purchase #6 $95.89   5.825%   $101.4756   $101.48   $101.50   $101.50  
  Purchase #7 $200.52   4.113%   $208.7674   $208.77   $208.75   $208.80  
  7 purchase totals = $929.75       $1,014.1457   $1,014.16   $1,014.15   $1,014.30