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 $183.80   9.385%   $201.0496   $201.05   $201.05   $201.00  
  Purchase #2 $182.93   9.148%   $199.6644   $199.66   $199.65   $199.70  
  Purchase #3 $82.35   6.354%   $87.5825   $87.58   $87.60   $87.60  
  Purchase #4 $63.33   8.679%   $68.8264   $68.83   $68.85   $68.80  
  Purchase #5 $51.57   3.860%   $53.5606   $53.56   $53.55   $53.60  
  Purchase #6 $183.34   6.593%   $195.4276   $195.43   $195.45   $195.40  
  Purchase #7 $9.55   10.237%   $10.5276   $10.53   $10.55   $10.50  
  7 purchase totals = $756.87       $816.6387   $816.64   $816.70   $816.60