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 $58.84   5.527%   $62.0921   $62.09   $62.10   $62.10  
  Purchase #2 $210.99   3.422%   $218.2101   $218.21   $218.20   $218.20  
  Purchase #3 $234.74   7.834%   $253.1295   $253.13   $253.15   $253.10  
  Purchase #4 $68.45   10.182%   $75.4196   $75.42   $75.40   $75.40  
  Purchase #5 $184.74   10.452%   $204.049   $204.05   $204.05   $204.00  
  Purchase #6 $184.42   12.431%   $207.3453   $207.35   $207.35   $207.30  
  Purchase #7 $41.90   12.317%   $47.0608   $47.06   $47.05   $47.10  
  7 purchase totals = $984.08       $1,067.3064   $1,067.31   $1,067.30   $1,067.20