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 $41.55   5.799%   $43.9595   $43.96   $43.95   $44.00  
  Purchase #2 $78.75   5.148%   $82.8041   $82.80   $82.80   $82.80  
  Purchase #3 $112.61   11.740%   $125.8304   $125.83   $125.85   $125.80  
  Purchase #4 $166.39   6.424%   $177.0789   $177.08   $177.10   $177.10  
  Purchase #5 $16.80   5.105%   $17.6576   $17.66   $17.65   $17.70  
  Purchase #6 $244.81   9.247%   $267.4476   $267.45   $267.45   $267.40  
  Purchase #7 $42.83   7.553%   $46.0649   $46.06   $46.05   $46.10  
  7 purchase totals = $703.74       $760.8430   $760.84   $760.85   $760.90