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 $75.61   13.256%   $85.6329   $85.63   $85.65   $85.60  
  Purchase #2 $184.51   12.518%   $207.607   $207.61   $207.60   $207.60  
  Purchase #3 $147.48   9.233%   $161.0968   $161.10   $161.10   $161.10  
  Purchase #4 $73.35   8.631%   $79.6808   $79.68   $79.70   $79.70  
  Purchase #5 $214.56   10.579%   $237.2583   $237.26   $237.25   $237.30  
  Purchase #6 $218.92   5.190%   $230.2819   $230.28   $230.30   $230.30  
  Purchase #7 $98.55   6.555%   $105.01   $105.01   $105.00   $105.00  
  7 purchase totals = $1,012.98       $1,106.5677   $1,106.57   $1,106.60   $1,106.60