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 $244.31   8.479%   $265.025   $265.03   $265.05   $265.00  
  Purchase #2 $42.34   9.152%   $46.215   $46.22   $46.20   $46.20  
  Purchase #3 $80.55   10.337%   $88.8765   $88.88   $88.90   $88.90  
  Purchase #4 $36.99   9.178%   $40.3849   $40.38   $40.40   $40.40  
  Purchase #5 $191.66   13.831%   $218.1685   $218.17   $218.15   $218.20  
  Purchase #6 $232.89   8.850%   $253.5008   $253.50   $253.50   $253.50  
  Purchase #7 $156.45   3.433%   $161.8209   $161.82   $161.80   $161.80  
  7 purchase totals = $985.19       $1,073.9916   $1,074.00   $1,074.00   $1,074.00