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 $181.94   6.858%   $194.4174   $194.42   $194.40   $194.40  
  Purchase #2 $24.59   4.541%   $25.7066   $25.71   $25.70   $25.70  
  Purchase #3 $53.34   5.167%   $56.0961   $56.10   $56.10   $56.10  
  Purchase #4 $67.28   11.110%   $74.7548   $74.75   $74.75   $74.80  
  Purchase #5 $177.27   10.280%   $195.4934   $195.49   $195.50   $195.50  
  Purchase #6 $204.68   5.718%   $216.3836   $216.38   $216.40   $216.40  
  Purchase #7 $236.66   6.482%   $252.0003   $252.00   $252.00   $252.00  
  7 purchase totals = $945.76       $1,014.8522   $1,014.85   $1,014.85   $1,014.90