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 $35.53   4.809%   $37.2386   $37.24   $37.25   $37.20  
  Purchase #2 $90.47   4.568%   $94.6027   $94.60   $94.60   $94.60  
  Purchase #3 $156.84   7.743%   $168.9841   $168.98   $169.00   $169.00  
  Purchase #4 $229.76   5.359%   $242.0728   $242.07   $242.05   $242.10  
  Purchase #5 $62.84   9.724%   $68.9506   $68.95   $68.95   $69.00  
  Purchase #6 $233.67   11.301%   $260.077   $260.08   $260.10   $260.10  
  Purchase #7 $214.69   4.603%   $224.5722   $224.57   $224.55   $224.60  
  7 purchase totals = $1,023.80       $1,096.4980   $1,096.49   $1,096.50   $1,096.60