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 $69.28   9.588%   $75.9226   $75.92   $75.90   $75.90  
  Purchase #2 $224.36   4.727%   $234.9655   $234.97   $234.95   $235.00  
  Purchase #3 $178.46   9.315%   $195.0835   $195.08   $195.10   $195.10  
  Purchase #4 $222.52   11.569%   $248.2633   $248.26   $248.25   $248.30  
  Purchase #5 $48.60   12.294%   $54.5749   $54.57   $54.55   $54.60  
  Purchase #6 $236.45   10.812%   $262.015   $262.02   $262.00   $262.00  
  Purchase #7 $62.46   4.839%   $65.4824   $65.48   $65.50   $65.50  
  7 purchase totals = $1,042.13       $1,136.3072   $1,136.30   $1,136.25   $1,136.40