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 $196.42   10.453%   $216.9518   $216.95   $216.95   $217.00  
  Purchase #2 $38.51   7.656%   $41.4583   $41.46   $41.45   $41.50  
  Purchase #3 $156.65   11.122%   $174.0726   $174.07   $174.05   $174.10  
  Purchase #4 $84.56   10.114%   $93.1124   $93.11   $93.10   $93.10  
  Purchase #5 $207.26   4.436%   $216.4541   $216.45   $216.45   $216.50  
  Purchase #6 $248.53   10.820%   $275.4209   $275.42   $275.40   $275.40  
  Purchase #7 $21.49   11.138%   $23.8836   $23.88   $23.90   $23.90  
  7 purchase totals = $953.42       $1,041.3537   $1,041.34   $1,041.30   $1,041.50