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 $22.38   5.817%   $23.6818   $23.68   $23.70   $23.70  
  Purchase #2 $238.94   11.430%   $266.2508   $266.25   $266.25   $266.30  
  Purchase #3 $168.36   3.705%   $174.5977   $174.60   $174.60   $174.60  
  Purchase #4 $50.65   4.622%   $52.991   $52.99   $53.00   $53.00  
  Purchase #5 $229.36   9.553%   $251.2708   $251.27   $251.25   $251.30  
  Purchase #6 $205.40   6.304%   $218.3484   $218.35   $218.35   $218.30  
  Purchase #7 $73.66   3.672%   $76.3648   $76.36   $76.35   $76.40  
  7 purchase totals = $988.75       $1,063.5053   $1,063.50   $1,063.50   $1,063.60