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 $153.42   13.425%   $174.0166   $174.02   $174.00   $174.00  
  Purchase #2 $192.67   9.785%   $211.5228   $211.52   $211.50   $211.50  
  Purchase #3 $217.26   8.198%   $235.071   $235.07   $235.05   $235.10  
  Purchase #4 $176.62   9.243%   $192.945   $192.95   $192.95   $192.90  
  Purchase #5 $161.87   7.684%   $174.3081   $174.31   $174.30   $174.30  
  Purchase #6 $201.44   5.571%   $212.6622   $212.66   $212.65   $212.70  
  Purchase #7 $61.66   3.680%   $63.9291   $63.93   $63.95   $63.90  
  7 purchase totals = $1,164.94       $1,264.4548   $1,264.46   $1,264.40   $1,264.40