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 $86.77   10.271%   $95.6821   $95.68   $95.70   $95.70  
  Purchase #2 $212.58   5.363%   $223.9807   $223.98   $224.00   $224.00  
  Purchase #3 $121.89   6.232%   $129.4862   $129.49   $129.50   $129.50  
  Purchase #4 $13.46   9.401%   $14.7254   $14.73   $14.75   $14.70  
  Purchase #5 $100.25   8.830%   $109.1021   $109.10   $109.10   $109.10  
  Purchase #6 $198.66   5.237%   $209.0638   $209.06   $209.05   $209.10  
  Purchase #7 $97.26   3.650%   $100.81   $100.81   $100.80   $100.80  
  7 purchase totals = $830.87       $882.8503   $882.85   $882.90   $882.90