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 $206.97   3.237%   $213.6696   $213.67   $213.65   $213.70  
  Purchase #2 $88.95   11.130%   $98.8501   $98.85   $98.85   $98.90  
  Purchase #3 $60.38   4.690%   $63.2118   $63.21   $63.20   $63.20  
  Purchase #4 $96.42   4.176%   $100.4465   $100.45   $100.45   $100.40  
  Purchase #5 $169.30   6.411%   $180.1538   $180.15   $180.15   $180.20  
  Purchase #6 $179.31   7.203%   $192.2257   $192.23   $192.25   $192.20  
  Purchase #7 $210.64   7.289%   $225.9935   $225.99   $226.00   $226.00  
  7 purchase totals = $1,011.97       $1,074.5510   $1,074.55   $1,074.55   $1,074.60