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 $177.33   9.761%   $194.6392   $194.64   $194.65   $194.60  
  Purchase #2 $231.35   9.377%   $253.0437   $253.04   $253.05   $253.00  
  Purchase #3 $174.83   12.657%   $196.9582   $196.96   $196.95   $197.00  
  Purchase #4 $53.28   13.848%   $60.6582   $60.66   $60.65   $60.70  
  Purchase #5 $231.63   4.264%   $241.5067   $241.51   $241.50   $241.50  
  Purchase #6 $188.81   5.546%   $199.2814   $199.28   $199.30   $199.30  
  Purchase #7 $242.46   11.680%   $270.7793   $270.78   $270.80   $270.80  
  7 purchase totals = $1,299.69       $1,416.8667   $1,416.87   $1,416.90   $1,416.90