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 $60.69   3.548%   $62.8433   $62.84   $62.85   $62.80  
  Purchase #2 $144.28   12.117%   $161.7624   $161.76   $161.75   $161.80  
  Purchase #3 $176.49   4.230%   $183.9555   $183.96   $183.95   $184.00  
  Purchase #4 $139.30   7.547%   $149.813   $149.81   $149.80   $149.80  
  Purchase #5 $91.43   13.355%   $103.6405   $103.64   $103.65   $103.60  
  Purchase #6 $236.66   7.301%   $253.9385   $253.94   $253.95   $253.90  
  Purchase #7 $97.64   9.403%   $106.8211   $106.82   $106.80   $106.80  
  7 purchase totals = $946.49       $1,022.7743   $1,022.77   $1,022.75   $1,022.70