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 $193.33   10.690%   $213.997   $214.00   $214.00   $214.00  
  Purchase #2 $194.54   5.773%   $205.7708   $205.77   $205.75   $205.80  
  Purchase #3 $54.89   10.867%   $60.8549   $60.85   $60.85   $60.90  
  Purchase #4 $153.25   3.222%   $158.1877   $158.19   $158.20   $158.20  
  Purchase #5 $48.32   13.811%   $54.9935   $54.99   $55.00   $55.00  
  Purchase #6 $57.48   10.843%   $63.7126   $63.71   $63.70   $63.70  
  Purchase #7 $73.94   4.154%   $77.0115   $77.01   $77.00   $77.00  
  7 purchase totals = $775.75       $834.5280   $834.52   $834.50   $834.60