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 $193.76   11.478%   $215.9998   $216.00   $216.00   $216.00  
  Purchase #2 $178.27   6.246%   $189.4047   $189.40   $189.40   $189.40  
  Purchase #3 $57.62   6.394%   $61.3042   $61.30   $61.30   $61.30  
  Purchase #4 $177.62   3.838%   $184.4371   $184.44   $184.45   $184.40  
  Purchase #5 $129.58   11.450%   $144.4169   $144.42   $144.40   $144.40  
  Purchase #6 $197.46   8.854%   $214.9431   $214.94   $214.95   $214.90  
  Purchase #7 $88.98   4.598%   $93.0713   $93.07   $93.05   $93.10  
  7 purchase totals = $1,023.29       $1,103.5771   $1,103.57   $1,103.55   $1,103.50