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 $43.29   8.802%   $47.1004   $47.10   $47.10   $47.10  
  Purchase #2 $234.44   7.346%   $251.662   $251.66   $251.65   $251.70  
  Purchase #3 $240.91   9.399%   $263.5531   $263.55   $263.55   $263.60  
  Purchase #4 $98.31   13.552%   $111.633   $111.63   $111.65   $111.60  
  Purchase #5 $171.50   13.751%   $195.083   $195.08   $195.10   $195.10  
  Purchase #6 $151.95   9.247%   $166.0008   $166.00   $166.00   $166.00  
  Purchase #7 $69.83   9.193%   $76.2495   $76.25   $76.25   $76.20  
  7 purchase totals = $1,010.23       $1,111.2818   $1,111.27   $1,111.30   $1,111.30