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 $86.68   10.297%   $95.6054   $95.61   $95.60   $95.60  
  Purchase #2 $67.74   6.307%   $72.0124   $72.01   $72.00   $72.00  
  Purchase #3 $114.99   13.616%   $130.647   $130.65   $130.65   $130.60  
  Purchase #4 $190.48   10.627%   $210.7223   $210.72   $210.70   $210.70  
  Purchase #5 $247.82   9.733%   $271.9403   $271.94   $271.95   $271.90  
  Purchase #6 $186.81   12.867%   $210.8468   $210.85   $210.85   $210.80  
  Purchase #7 $230.83   9.414%   $252.5603   $252.56   $252.55   $252.60  
  7 purchase totals = $1,125.35       $1,244.3345   $1,244.34   $1,244.30   $1,244.20