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 $213.75   5.797%   $226.1411   $226.14   $226.15   $226.10  
  Purchase #2 $187.33   8.233%   $202.7529   $202.75   $202.75   $202.80  
  Purchase #3 $158.72   5.380%   $167.2591   $167.26   $167.25   $167.30  
  Purchase #4 $51.29   7.693%   $55.2357   $55.24   $55.25   $55.20  
  Purchase #5 $147.76   13.383%   $167.5347   $167.53   $167.55   $167.50  
  Purchase #6 $189.42   12.136%   $212.408   $212.41   $212.40   $212.40  
  Purchase #7 $168.82   3.129%   $174.1024   $174.10   $174.10   $174.10  
  7 purchase totals = $1,117.09       $1,205.4339   $1,205.43   $1,205.45   $1,205.40