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 $67.34   11.287%   $74.9407   $74.94   $74.95   $74.90  
  Purchase #2 $206.78   7.207%   $221.6826   $221.68   $221.70   $221.70  
  Purchase #3 $167.40   5.484%   $176.5802   $176.58   $176.60   $176.60  
  Purchase #4 $235.60   9.464%   $257.8972   $257.90   $257.90   $257.90  
  Purchase #5 $48.30   7.269%   $51.8109   $51.81   $51.80   $51.80  
  Purchase #6 $180.75   8.155%   $195.4902   $195.49   $195.50   $195.50  
  Purchase #7 $111.36   5.391%   $117.3634   $117.36   $117.35   $117.40  
  7 purchase totals = $1,017.53       $1,095.7652   $1,095.76   $1,095.80   $1,095.80