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 $49.29   9.432%   $53.939   $53.94   $53.95   $53.90  
  Purchase #2 $240.63   13.398%   $272.8696   $272.87   $272.85   $272.90  
  Purchase #3 $120.88   13.474%   $137.1674   $137.17   $137.15   $137.20  
  Purchase #4 $201.51   4.794%   $211.1704   $211.17   $211.15   $211.20  
  Purchase #5 $120.47   8.203%   $130.3522   $130.35   $130.35   $130.40  
  Purchase #6 $61.72   12.328%   $69.3288   $69.33   $69.35   $69.30  
  Purchase #7 $244.66   9.668%   $268.3137   $268.31   $268.30   $268.30  
  7 purchase totals = $1,039.16       $1,143.1411   $1,143.14   $1,143.10   $1,143.20