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 $141.39   10.793%   $156.6502   $156.65   $156.65   $156.70  
  Purchase #2 $241.61   10.777%   $267.6483   $267.65   $267.65   $267.60  
  Purchase #3 $227.97   7.496%   $245.0586   $245.06   $245.05   $245.10  
  Purchase #4 $188.87   7.838%   $203.6736   $203.67   $203.65   $203.70  
  Purchase #5 $168.47   12.754%   $189.9567   $189.96   $189.95   $190.00  
  Purchase #6 $109.94   8.768%   $119.5795   $119.58   $119.60   $119.60  
  Purchase #7 $24.78   4.489%   $25.8924   $25.89   $25.90   $25.90  
  7 purchase totals = $1,103.03       $1,208.4593   $1,208.46   $1,208.45   $1,208.60