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 $89.94   6.707%   $95.9723   $95.97   $95.95   $96.00  
  Purchase #2 $237.60   3.670%   $246.3199   $246.32   $246.30   $246.30  
  Purchase #3 $59.94   9.456%   $65.6079   $65.61   $65.60   $65.60  
  Purchase #4 $70.50   9.572%   $77.2483   $77.25   $77.25   $77.20  
  Purchase #5 $162.60   12.289%   $182.5819   $182.58   $182.60   $182.60  
  Purchase #6 $150.88   13.302%   $170.9501   $170.95   $170.95   $171.00  
  Purchase #7 $106.74   6.686%   $113.8766   $113.88   $113.90   $113.90  
  7 purchase totals = $878.20       $952.5570   $952.56   $952.55   $952.60