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 $42.63   8.532%   $46.2672   $46.27   $46.25   $46.30  
  Purchase #2 $177.92   10.678%   $196.9183   $196.92   $196.90   $196.90  
  Purchase #3 $226.58   9.761%   $248.6965   $248.70   $248.70   $248.70  
  Purchase #4 $54.65   10.512%   $60.3948   $60.39   $60.40   $60.40  
  Purchase #5 $161.30   3.288%   $166.6035   $166.60   $166.60   $166.60  
  Purchase #6 $137.46   3.295%   $141.9893   $141.99   $142.00   $142.00  
  Purchase #7 $212.31   10.456%   $234.5091   $234.51   $234.50   $234.50  
  7 purchase totals = $1,012.85       $1,095.3787   $1,095.38   $1,095.35   $1,095.40