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 $245.36   9.233%   $268.0141   $268.01   $268.00   $268.00  
  Purchase #2 $96.43   11.580%   $107.5966   $107.60   $107.60   $107.60  
  Purchase #3 $22.49   7.324%   $24.1372   $24.14   $24.15   $24.10  
  Purchase #4 $103.62   13.262%   $117.3621   $117.36   $117.35   $117.40  
  Purchase #5 $238.47   9.667%   $261.5229   $261.52   $261.50   $261.50  
  Purchase #6 $209.66   7.444%   $225.2671   $225.27   $225.25   $225.30  
  Purchase #7 $235.89   6.694%   $251.6805   $251.68   $251.70   $251.70  
  7 purchase totals = $1,151.92       $1,255.5805   $1,255.58   $1,255.55   $1,255.60