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 $61.47   12.388%   $69.0849   $69.08   $69.10   $69.10  
  Purchase #2 $224.94   4.402%   $234.8419   $234.84   $234.85   $234.80  
  Purchase #3 $121.92   7.699%   $131.3066   $131.31   $131.30   $131.30  
  Purchase #4 $200.85   7.344%   $215.6004   $215.60   $215.60   $215.60  
  Purchase #5 $52.42   3.439%   $54.2227   $54.22   $54.20   $54.20  
  Purchase #6 $171.39   8.198%   $185.4406   $185.44   $185.45   $185.40  
  Purchase #7 $58.78   3.697%   $60.9531   $60.95   $60.95   $61.00  
  7 purchase totals = $891.77       $951.4502   $951.44   $951.45   $951.40