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 $62.68   10.260%   $69.111   $69.11   $69.10   $69.10  
  Purchase #2 $106.82   9.628%   $117.1046   $117.10   $117.10   $117.10  
  Purchase #3 $177.54   8.107%   $191.9332   $191.93   $191.95   $191.90  
  Purchase #4 $57.78   7.720%   $62.2406   $62.24   $62.25   $62.20  
  Purchase #5 $217.41   9.852%   $238.8292   $238.83   $238.85   $238.80  
  Purchase #6 $122.74   10.111%   $135.1502   $135.15   $135.15   $135.20  
  Purchase #7 $178.99   8.434%   $194.086   $194.09   $194.10   $194.10  
  7 purchase totals = $923.96       $1,008.4548   $1,008.45   $1,008.50   $1,008.40