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 $88.36   6.214%   $93.8507   $93.85   $93.85   $93.90  
  Purchase #2 $198.74   10.829%   $220.2616   $220.26   $220.25   $220.30  
  Purchase #3 $60.98   6.366%   $64.862   $64.86   $64.85   $64.90  
  Purchase #4 $226.77   5.448%   $239.1244   $239.12   $239.10   $239.10  
  Purchase #5 $78.61   5.105%   $82.623   $82.62   $82.60   $82.60  
  Purchase #6 $172.52   6.163%   $183.1524   $183.15   $183.15   $183.20  
  Purchase #7 $60.78   13.491%   $68.9798   $68.98   $69.00   $69.00  
  7 purchase totals = $886.76       $952.8539   $952.84   $952.80   $953.00