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 $62.27   4.862%   $65.2976   $65.30   $65.30   $65.30  
  Purchase #2 $107.88   7.772%   $116.2644   $116.26   $116.25   $116.30  
  Purchase #3 $175.25   6.460%   $186.5712   $186.57   $186.55   $186.60  
  Purchase #4 $39.55   10.198%   $43.5833   $43.58   $43.60   $43.60  
  Purchase #5 $38.55   5.451%   $40.6514   $40.65   $40.65   $40.70  
  Purchase #6 $200.74   6.244%   $213.2742   $213.27   $213.25   $213.30  
  Purchase #7 $81.68   3.677%   $84.6834   $84.68   $84.70   $84.70  
  7 purchase totals = $705.92       $750.3255   $750.31   $750.30   $750.50