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 $69.68   11.832%   $77.9245   $77.92   $77.90   $77.90  
  Purchase #2 $83.70   12.831%   $94.4395   $94.44   $94.45   $94.40  
  Purchase #3 $12.96   4.429%   $13.534   $13.53   $13.55   $13.50  
  Purchase #4 $59.54   8.328%   $64.4985   $64.50   $64.50   $64.50  
  Purchase #5 $88.63   9.556%   $97.0995   $97.10   $97.10   $97.10  
  Purchase #6 $41.53   13.205%   $47.014   $47.01   $47.00   $47.00  
  Purchase #7 $61.92   8.349%   $67.0897   $67.09   $67.10   $67.10  
  7 purchase totals = $417.96       $461.5997   $461.59   $461.60   $461.50