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 $65.27   4.561%   $68.247   $68.25   $68.25   $68.20  
  Purchase #2 $118.50   5.739%   $125.3007   $125.30   $125.30   $125.30  
  Purchase #3 $111.60   11.686%   $124.6416   $124.64   $124.65   $124.60  
  Purchase #4 $164.59   8.639%   $178.8089   $178.81   $178.80   $178.80  
  Purchase #5 $243.92   10.500%   $269.5316   $269.53   $269.55   $269.50  
  Purchase #6 $60.34   5.369%   $63.5797   $63.58   $63.60   $63.60  
  Purchase #7 $128.47   8.720%   $139.6726   $139.67   $139.65   $139.70  
  7 purchase totals = $892.69       $969.7821   $969.78   $969.80   $969.70