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 $90.67   5.176%   $95.3631   $95.36   $95.35   $95.40  
  Purchase #2 $48.64   7.126%   $52.1061   $52.11   $52.10   $52.10  
  Purchase #3 $6.75   11.837%   $7.549   $7.55   $7.55   $7.50  
  Purchase #4 $175.40   10.402%   $193.6451   $193.65   $193.65   $193.60  
  Purchase #5 $185.92   4.375%   $194.054   $194.05   $194.05   $194.10  
  Purchase #6 $245.28   12.186%   $275.1698   $275.17   $275.15   $275.20  
  Purchase #7 $152.32   10.313%   $168.0288   $168.03   $168.05   $168.00  
  7 purchase totals = $904.98       $985.9159   $985.92   $985.90   $985.90