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 $70.96   7.310%   $76.1472   $76.15   $76.15   $76.10  
  Purchase #2 $69.88   7.186%   $74.9016   $74.90   $74.90   $74.90  
  Purchase #3 $121.66   4.104%   $126.6529   $126.65   $126.65   $126.70  
  Purchase #4 $234.58   4.164%   $244.3479   $244.35   $244.35   $244.30  
  Purchase #5 $166.47   11.364%   $185.3877   $185.39   $185.40   $185.40  
  Purchase #6 $224.33   3.396%   $231.9482   $231.95   $231.95   $231.90  
  Purchase #7 $173.26   3.110%   $178.6484   $178.65   $178.65   $178.60  
  7 purchase totals = $1,061.14       $1,118.0339   $1,118.04   $1,118.05   $1,117.90