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 $226.55   7.804%   $244.23   $244.23   $244.25   $244.20  
  Purchase #2 $61.27   5.182%   $64.445   $64.45   $64.45   $64.40  
  Purchase #3 $167.86   4.869%   $176.0331   $176.03   $176.05   $176.00  
  Purchase #4 $207.48   6.641%   $221.2587   $221.26   $221.25   $221.30  
  Purchase #5 $201.65   3.482%   $208.6715   $208.67   $208.65   $208.70  
  Purchase #6 $52.69   9.232%   $57.5543   $57.55   $57.55   $57.60  
  Purchase #7 $219.95   9.753%   $241.4017   $241.40   $241.40   $241.40  
  7 purchase totals = $1,137.45       $1,213.5943   $1,213.59   $1,213.60   $1,213.60