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 $136.51   10.671%   $151.077   $151.08   $151.10   $151.10  
  Purchase #2 $156.66   12.268%   $175.879   $175.88   $175.90   $175.90  
  Purchase #3 $86.36   7.810%   $93.1047   $93.10   $93.10   $93.10  
  Purchase #4 $54.48   9.705%   $59.7673   $59.77   $59.75   $59.80  
  Purchase #5 $205.74   6.385%   $218.8765   $218.88   $218.90   $218.90  
  Purchase #6 $226.44   5.378%   $238.6179   $238.62   $238.60   $238.60  
  Purchase #7 $16.84   7.429%   $18.091   $18.09   $18.10   $18.10  
  7 purchase totals = $883.03       $955.4134   $955.42   $955.45   $955.50