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 $188.87   13.332%   $214.0501   $214.05   $214.05   $214.10  
  Purchase #2 $39.72   4.818%   $41.6337   $41.63   $41.65   $41.60  
  Purchase #3 $138.31   9.725%   $151.7606   $151.76   $151.75   $151.80  
  Purchase #4 $8.98   6.694%   $9.5811   $9.58   $9.60   $9.60  
  Purchase #5 $161.89   8.414%   $175.5114   $175.51   $175.50   $175.50  
  Purchase #6 $196.95   13.743%   $224.0168   $224.02   $224.00   $224.00  
  Purchase #7 $187.26   5.395%   $197.3627   $197.36   $197.35   $197.40  
  7 purchase totals = $921.98       $1,013.9164   $1,013.91   $1,013.90   $1,014.00