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 $209.66   6.802%   $223.9211   $223.92   $223.90   $223.90  
  Purchase #2 $51.84   3.614%   $53.7135   $53.71   $53.70   $53.70  
  Purchase #3 $191.30   11.595%   $213.4812   $213.48   $213.50   $213.50  
  Purchase #4 $136.91   10.201%   $150.8762   $150.88   $150.90   $150.90  
  Purchase #5 $166.98   8.749%   $181.5891   $181.59   $181.60   $181.60  
  Purchase #6 $162.61   7.716%   $175.157   $175.16   $175.15   $175.20  
  Purchase #7 $190.37   8.716%   $206.9626   $206.96   $206.95   $207.00  
  7 purchase totals = $1,109.67       $1,205.7007   $1,205.70   $1,205.70   $1,205.80