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 $195.32   9.543%   $213.9594   $213.96   $213.95   $214.00  
  Purchase #2 $61.46   8.277%   $66.547   $66.55   $66.55   $66.50  
  Purchase #3 $225.33   9.295%   $246.2744   $246.27   $246.25   $246.30  
  Purchase #4 $10.97   6.773%   $11.713   $11.71   $11.70   $11.70  
  Purchase #5 $209.84   7.388%   $225.343   $225.34   $225.35   $225.30  
  Purchase #6 $150.75   10.212%   $166.1446   $166.14   $166.15   $166.10  
  Purchase #7 $82.97   6.175%   $88.0934   $88.09   $88.10   $88.10  
  7 purchase totals = $936.64       $1,018.0748   $1,018.06   $1,018.05   $1,018.00