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 $58.61   8.542%   $63.6165   $63.62   $63.60   $63.60  
  Purchase #2 $95.56   5.109%   $100.4422   $100.44   $100.45   $100.40  
  Purchase #3 $43.92   6.784%   $46.8995   $46.90   $46.90   $46.90  
  Purchase #4 $63.27   3.232%   $65.3149   $65.31   $65.30   $65.30  
  Purchase #5 $183.53   4.688%   $192.1339   $192.13   $192.15   $192.10  
  Purchase #6 $69.62   8.377%   $75.4521   $75.45   $75.45   $75.50  
  Purchase #7 $105.57   5.286%   $111.1504   $111.15   $111.15   $111.20  
  7 purchase totals = $620.08       $655.0095   $655.00   $655.00   $655.00