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 $64.73   13.852%   $73.6964   $73.70   $73.70   $73.70  
  Purchase #2 $49.86   4.353%   $52.0304   $52.03   $52.05   $52.00  
  Purchase #3 $191.79   8.776%   $208.6215   $208.62   $208.60   $208.60  
  Purchase #4 $41.76   10.565%   $46.1719   $46.17   $46.15   $46.20  
  Purchase #5 $213.41   4.867%   $223.7967   $223.80   $223.80   $223.80  
  Purchase #6 $108.34   6.704%   $115.6031   $115.60   $115.60   $115.60  
  Purchase #7 $218.82   4.369%   $228.3802   $228.38   $228.40   $228.40  
  7 purchase totals = $888.71       $948.3002   $948.30   $948.30   $948.30