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 $86.87   11.615%   $96.96   $96.96   $96.95   $97.00  
  Purchase #2 $218.58   12.822%   $246.6063   $246.61   $246.60   $246.60  
  Purchase #3 $249.81   7.176%   $267.7364   $267.74   $267.75   $267.70  
  Purchase #4 $241.37   8.184%   $261.1237   $261.12   $261.10   $261.10  
  Purchase #5 $10.43   10.610%   $11.5366   $11.54   $11.55   $11.50  
  Purchase #6 $235.93   7.287%   $253.1222   $253.12   $253.10   $253.10  
  Purchase #7 $62.67   9.140%   $68.398   $68.40   $68.40   $68.40  
  7 purchase totals = $1,105.66       $1,205.4832   $1,205.49   $1,205.45   $1,205.40