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 $50.74   4.330%   $52.937   $52.94   $52.95   $52.90  
  Purchase #2 $168.74   3.842%   $175.223   $175.22   $175.20   $175.20  
  Purchase #3 $223.63   5.652%   $236.2696   $236.27   $236.25   $236.30  
  Purchase #4 $128.35   6.582%   $136.798   $136.80   $136.80   $136.80  
  Purchase #5 $126.29   4.706%   $132.2332   $132.23   $132.25   $132.20  
  Purchase #6 $39.44   9.655%   $43.2479   $43.25   $43.25   $43.20  
  Purchase #7 $249.96   11.641%   $279.0578   $279.06   $279.05   $279.10  
  7 purchase totals = $987.15       $1,055.7665   $1,055.77   $1,055.75   $1,055.70