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 $58.58   5.128%   $61.584   $61.58   $61.60   $61.60  
  Purchase #2 $77.85   12.821%   $87.8311   $87.83   $87.85   $87.80  
  Purchase #3 $127.78   3.121%   $131.768   $131.77   $131.75   $131.80  
  Purchase #4 $166.84   3.135%   $172.0704   $172.07   $172.05   $172.10  
  Purchase #5 $42.60   4.671%   $44.5898   $44.59   $44.60   $44.60  
  Purchase #6 $234.97   8.166%   $254.1577   $254.16   $254.15   $254.20  
  Purchase #7 $105.95   4.725%   $110.9561   $110.96   $110.95   $111.00  
  7 purchase totals = $814.57       $862.9571   $862.96   $862.95   $863.10