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 $65.87   8.528%   $71.4874   $71.49   $71.50   $71.50  
  Purchase #2 $243.54   10.560%   $269.2578   $269.26   $269.25   $269.30  
  Purchase #3 $183.33   4.380%   $191.3599   $191.36   $191.35   $191.40  
  Purchase #4 $237.66   7.573%   $255.658   $255.66   $255.65   $255.70  
  Purchase #5 $76.83   13.276%   $87.03   $87.03   $87.05   $87.00  
  Purchase #6 $37.37   10.285%   $41.2135   $41.21   $41.20   $41.20  
  Purchase #7 $34.64   9.745%   $38.0157   $38.02   $38.00   $38.00  
  7 purchase totals = $879.24       $954.0223   $954.03   $954.00   $954.10