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 $87.64   9.704%   $96.1446   $96.14   $96.15   $96.10  
  Purchase #2 $175.78   10.715%   $194.6148   $194.61   $194.60   $194.60  
  Purchase #3 $190.67   3.321%   $197.0022   $197.00   $197.00   $197.00  
  Purchase #4 $244.49   8.366%   $264.944   $264.94   $264.95   $264.90  
  Purchase #5 $132.53   4.138%   $138.0141   $138.01   $138.00   $138.00  
  Purchase #6 $59.38   10.303%   $65.4979   $65.50   $65.50   $65.50  
  Purchase #7 $214.89   5.585%   $226.8916   $226.89   $226.90   $226.90  
  7 purchase totals = $1,105.38       $1,183.1092   $1,183.09   $1,183.10   $1,183.00