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 $68.42   11.193%   $76.0783   $76.08   $76.10   $76.10  
  Purchase #2 $202.62   13.446%   $229.8643   $229.86   $229.85   $229.90  
  Purchase #3 $55.62   3.864%   $57.7692   $57.77   $57.75   $57.80  
  Purchase #4 $245.99   12.435%   $276.5789   $276.58   $276.60   $276.60  
  Purchase #5 $44.75   9.627%   $49.0581   $49.06   $49.05   $49.10  
  Purchase #6 $237.55   11.572%   $265.0393   $265.04   $265.05   $265.00  
  Purchase #7 $210.33   5.294%   $221.4649   $221.46   $221.45   $221.50  
  7 purchase totals = $1,065.28       $1,175.8530   $1,175.85   $1,175.85   $1,176.00