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 $93.50   13.578%   $106.1954   $106.20   $106.20   $106.20  
  Purchase #2 $149.51   8.617%   $162.3933   $162.39   $162.40   $162.40  
  Purchase #3 $185.58   12.449%   $208.6829   $208.68   $208.70   $208.70  
  Purchase #4 $241.97   8.281%   $262.0075   $262.01   $262.00   $262.00  
  Purchase #5 $217.60   3.301%   $224.783   $224.78   $224.80   $224.80  
  Purchase #6 $238.45   8.483%   $258.6777   $258.68   $258.70   $258.70  
  Purchase #7 $165.98   8.315%   $179.7812   $179.78   $179.80   $179.80  
  7 purchase totals = $1,292.59       $1,402.5210   $1,402.52   $1,402.60   $1,402.60