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 $217.33   13.161%   $245.9328   $245.93   $245.95   $245.90  
  Purchase #2 $193.33   12.854%   $218.1806   $218.18   $218.20   $218.20  
  Purchase #3 $184.47   8.564%   $200.268   $200.27   $200.25   $200.30  
  Purchase #4 $194.59   6.150%   $206.5573   $206.56   $206.55   $206.60  
  Purchase #5 $34.98   4.199%   $36.4488   $36.45   $36.45   $36.40  
  Purchase #6 $192.72   9.344%   $210.7278   $210.73   $210.75   $210.70  
  Purchase #7 $183.42   11.727%   $204.9297   $204.93   $204.95   $204.90  
  7 purchase totals = $1,200.84       $1,323.0450   $1,323.05   $1,323.10   $1,323.00