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 $201.91   9.549%   $221.1904   $221.19   $221.20   $221.20  
  Purchase #2 $94.73   6.856%   $101.2247   $101.22   $101.20   $101.20  
  Purchase #3 $125.59   9.653%   $137.7132   $137.71   $137.70   $137.70  
  Purchase #4 $52.76   6.491%   $56.1847   $56.18   $56.20   $56.20  
  Purchase #5 $82.92   5.530%   $87.5055   $87.51   $87.50   $87.50  
  Purchase #6 $205.57   6.366%   $218.6566   $218.66   $218.65   $218.70  
  Purchase #7 $228.82   5.216%   $240.7553   $240.76   $240.75   $240.80  
  7 purchase totals = $992.30       $1,063.2304   $1,063.23   $1,063.20   $1,063.30