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 $44.39   4.844%   $46.5403   $46.54   $46.55   $46.50  
  Purchase #2 $144.46   11.538%   $161.1278   $161.13   $161.15   $161.10  
  Purchase #3 $192.43   3.185%   $198.5589   $198.56   $198.55   $198.60  
  Purchase #4 $222.70   9.525%   $243.9122   $243.91   $243.90   $243.90  
  Purchase #5 $221.80   8.821%   $241.365   $241.37   $241.35   $241.40  
  Purchase #6 $225.95   10.276%   $249.1686   $249.17   $249.15   $249.20  
  Purchase #7 $52.45   8.484%   $56.8999   $56.90   $56.90   $56.90  
  7 purchase totals = $1,104.18       $1,197.5727   $1,197.58   $1,197.55   $1,197.60