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 $101.43   5.767%   $107.2795   $107.28   $107.30   $107.30  
  Purchase #2 $239.87   9.668%   $263.0606   $263.06   $263.05   $263.10  
  Purchase #3 $82.34   8.423%   $89.2755   $89.28   $89.30   $89.30  
  Purchase #4 $161.81   3.727%   $167.8407   $167.84   $167.85   $167.80  
  Purchase #5 $60.50   5.553%   $63.8596   $63.86   $63.85   $63.90  
  Purchase #6 $229.73   13.205%   $260.0658   $260.07   $260.05   $260.10  
  Purchase #7 $208.76   7.500%   $224.417   $224.42   $224.40   $224.40  
  7 purchase totals = $1,084.44       $1,175.7987   $1,175.81   $1,175.80   $1,175.90