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 $191.83   5.399%   $202.1869   $202.19   $202.20   $202.20  
  Purchase #2 $211.48   13.446%   $239.9156   $239.92   $239.90   $239.90  
  Purchase #3 $93.28   13.858%   $106.2067   $106.21   $106.20   $106.20  
  Purchase #4 $47.53   12.869%   $53.6466   $53.65   $53.65   $53.60  
  Purchase #5 $180.91   10.832%   $200.5062   $200.51   $200.50   $200.50  
  Purchase #6 $53.77   4.358%   $56.1133   $56.11   $56.10   $56.10  
  Purchase #7 $151.30   3.201%   $156.1431   $156.14   $156.15   $156.10  
  7 purchase totals = $930.10       $1,014.7184   $1,014.73   $1,014.70   $1,014.60