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 $191.87   10.467%   $211.953   $211.95   $211.95   $212.00  
  Purchase #2 $82.59   5.453%   $87.0936   $87.09   $87.10   $87.10  
  Purchase #3 $171.28   12.324%   $192.3885   $192.39   $192.40   $192.40  
  Purchase #4 $79.91   8.411%   $86.6312   $86.63   $86.65   $86.60  
  Purchase #5 $228.52   9.168%   $249.4707   $249.47   $249.45   $249.50  
  Purchase #6 $247.38   6.191%   $262.6953   $262.70   $262.70   $262.70  
  Purchase #7 $155.69   13.817%   $177.2017   $177.20   $177.20   $177.20  
  7 purchase totals = $1,157.24       $1,267.4340   $1,267.43   $1,267.45   $1,267.50