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 $235.71   7.685%   $253.8243   $253.82   $253.80   $253.80  
  Purchase #2 $100.27   3.427%   $103.7063   $103.71   $103.70   $103.70  
  Purchase #3 $29.55   11.216%   $32.8643   $32.86   $32.85   $32.90  
  Purchase #4 $59.35   9.204%   $64.8126   $64.81   $64.80   $64.80  
  Purchase #5 $204.57   10.576%   $226.2053   $226.21   $226.20   $226.20  
  Purchase #6 $224.95   3.489%   $232.7985   $232.80   $232.80   $232.80  
  Purchase #7 $240.83   8.850%   $262.1435   $262.14   $262.15   $262.10  
  7 purchase totals = $1,095.23       $1,176.3548   $1,176.35   $1,176.30   $1,176.30