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 $87.61   9.534%   $95.9627   $95.96   $95.95   $96.00  
  Purchase #2 $156.72   11.540%   $174.8055   $174.81   $174.80   $174.80  
  Purchase #3 $157.33   4.359%   $164.188   $164.19   $164.20   $164.20  
  Purchase #4 $127.29   5.331%   $134.0758   $134.08   $134.10   $134.10  
  Purchase #5 $170.97   11.252%   $190.2075   $190.21   $190.20   $190.20  
  Purchase #6 $200.81   13.217%   $227.3511   $227.35   $227.35   $227.40  
  Purchase #7 $49.71   9.542%   $54.4533   $54.45   $54.45   $54.50  
  7 purchase totals = $950.44       $1,041.0439   $1,041.05   $1,041.05   $1,041.20