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 $67.53   8.449%   $73.2356   $73.24   $73.25   $73.20  
  Purchase #2 $160.67   4.445%   $167.8118   $167.81   $167.80   $167.80  
  Purchase #3 $236.99   7.112%   $253.8447   $253.84   $253.85   $253.80  
  Purchase #4 $205.94   3.730%   $213.6216   $213.62   $213.60   $213.60  
  Purchase #5 $142.62   8.869%   $155.269   $155.27   $155.25   $155.30  
  Purchase #6 $174.47   10.577%   $192.9237   $192.92   $192.90   $192.90  
  Purchase #7 $139.46   10.245%   $153.7477   $153.75   $153.75   $153.70  
  7 purchase totals = $1,127.68       $1,210.4541   $1,210.45   $1,210.40   $1,210.30