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 $183.84   12.576%   $206.9597   $206.96   $206.95   $207.00  
  Purchase #2 $202.53   8.770%   $220.2919   $220.29   $220.30   $220.30  
  Purchase #3 $88.92   8.129%   $96.1483   $96.15   $96.15   $96.10  
  Purchase #4 $164.70   3.488%   $170.4447   $170.44   $170.45   $170.40  
  Purchase #5 $161.98   12.209%   $181.7561   $181.76   $181.75   $181.80  
  Purchase #6 $161.63   7.623%   $173.9511   $173.95   $173.95   $174.00  
  Purchase #7 $190.48   8.421%   $206.5203   $206.52   $206.50   $206.50  
  7 purchase totals = $1,154.08       $1,256.0721   $1,256.07   $1,256.05   $1,256.10