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 $92.37   3.468%   $95.5734   $95.57   $95.55   $95.60  
  Purchase #2 $168.40   8.529%   $182.7628   $182.76   $182.75   $182.80  
  Purchase #3 $34.45   9.552%   $37.7407   $37.74   $37.75   $37.70  
  Purchase #4 $189.80   12.616%   $213.7452   $213.75   $213.75   $213.70  
  Purchase #5 $69.53   13.115%   $78.6489   $78.65   $78.65   $78.60  
  Purchase #6 $41.64   10.530%   $46.0247   $46.02   $46.00   $46.00  
  Purchase #7 $114.61   3.220%   $118.3004   $118.30   $118.30   $118.30  
  7 purchase totals = $710.80       $772.7961   $772.79   $772.75   $772.70