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 $211.89   10.723%   $234.611   $234.61   $234.60   $234.60  
  Purchase #2 $56.53   8.756%   $61.4798   $61.48   $61.50   $61.50  
  Purchase #3 $61.42   12.290%   $68.9685   $68.97   $68.95   $69.00  
  Purchase #4 $174.68   8.494%   $189.5173   $189.52   $189.50   $189.50  
  Purchase #5 $211.98   8.495%   $229.9877   $229.99   $230.00   $230.00  
  Purchase #6 $194.85   5.702%   $205.9603   $205.96   $205.95   $206.00  
  Purchase #7 $168.55   12.785%   $190.0991   $190.10   $190.10   $190.10  
  7 purchase totals = $1,079.90       $1,180.6237   $1,180.63   $1,180.60   $1,180.70