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 $56.61   10.510%   $62.5597   $62.56   $62.55   $62.60  
  Purchase #2 $202.70   4.306%   $211.4283   $211.43   $211.45   $211.40  
  Purchase #3 $146.92   9.650%   $161.0978   $161.10   $161.10   $161.10  
  Purchase #4 $177.55   6.631%   $189.3233   $189.32   $189.30   $189.30  
  Purchase #5 $195.69   13.509%   $222.1258   $222.13   $222.15   $222.10  
  Purchase #6 $177.61   8.201%   $192.1758   $192.18   $192.20   $192.20  
  Purchase #7 $236.30   5.634%   $249.6131   $249.61   $249.60   $249.60  
  7 purchase totals = $1,193.38       $1,288.3238   $1,288.33   $1,288.35   $1,288.30