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 $243.57   10.573%   $269.3227   $269.32   $269.30   $269.30  
  Purchase #2 $72.98   4.589%   $76.3291   $76.33   $76.35   $76.30  
  Purchase #3 $10.55   10.787%   $11.688   $11.69   $11.70   $11.70  
  Purchase #4 $218.71   4.482%   $228.5126   $228.51   $228.50   $228.50  
  Purchase #5 $163.68   4.131%   $170.4416   $170.44   $170.45   $170.40  
  Purchase #6 $180.36   10.149%   $198.6647   $198.66   $198.65   $198.70  
  Purchase #7 $204.27   11.258%   $227.2667   $227.27   $227.25   $227.30  
  7 purchase totals = $1,094.12       $1,182.2254   $1,182.22   $1,182.20   $1,182.20