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 $194.82   6.788%   $208.0444   $208.04   $208.05   $208.00  
  Purchase #2 $201.71   7.833%   $217.5099   $217.51   $217.50   $217.50  
  Purchase #3 $101.59   6.781%   $108.4788   $108.48   $108.50   $108.50  
  Purchase #4 $189.93   7.692%   $204.5394   $204.54   $204.55   $204.50  
  Purchase #5 $23.71   13.467%   $26.903   $26.90   $26.90   $26.90  
  Purchase #6 $154.37   7.772%   $166.3676   $166.37   $166.35   $166.40  
  Purchase #7 $202.39   7.441%   $217.4498   $217.45   $217.45   $217.40  
  7 purchase totals = $1,068.52       $1,149.2929   $1,149.29   $1,149.30   $1,149.20