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 $74.35   3.508%   $76.9582   $76.96   $76.95   $77.00  
  Purchase #2 $168.58   10.120%   $185.6403   $185.64   $185.65   $185.60  
  Purchase #3 $61.56   11.488%   $68.632   $68.63   $68.65   $68.60  
  Purchase #4 $99.49   9.623%   $109.0639   $109.06   $109.05   $109.10  
  Purchase #5 $134.75   12.489%   $151.5789   $151.58   $151.60   $151.60  
  Purchase #6 $207.40   12.669%   $233.6755   $233.68   $233.70   $233.70  
  Purchase #7 $206.29   3.307%   $213.112   $213.11   $213.10   $213.10  
  7 purchase totals = $952.42       $1,038.6608   $1,038.66   $1,038.70   $1,038.70