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 $208.33   12.660%   $234.7046   $234.70   $234.70   $234.70  
  Purchase #2 $158.60   3.816%   $164.6522   $164.65   $164.65   $164.70  
  Purchase #3 $24.43   10.805%   $27.0697   $27.07   $27.05   $27.10  
  Purchase #4 $105.32   9.243%   $115.0547   $115.05   $115.05   $115.10  
  Purchase #5 $152.78   7.150%   $163.7038   $163.70   $163.70   $163.70  
  Purchase #6 $235.52   3.687%   $244.2036   $244.20   $244.20   $244.20  
  Purchase #7 $228.45   7.232%   $244.9715   $244.97   $244.95   $245.00  
  7 purchase totals = $1,113.43       $1,194.3601   $1,194.34   $1,194.30   $1,194.50