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 $176.78   9.723%   $193.9683   $193.97   $193.95   $194.00  
  Purchase #2 $158.57   13.126%   $179.3839   $179.38   $179.40   $179.40  
  Purchase #3 $99.90   6.113%   $106.0069   $106.01   $106.00   $106.00  
  Purchase #4 $249.62   11.250%   $277.7023   $277.70   $277.70   $277.70  
  Purchase #5 $220.60   12.118%   $247.3323   $247.33   $247.35   $247.30  
  Purchase #6 $174.48   4.469%   $182.2775   $182.28   $182.30   $182.30  
  Purchase #7 $158.83   4.678%   $166.2601   $166.26   $166.25   $166.30  
  7 purchase totals = $1,238.78       $1,352.9313   $1,352.93   $1,352.95   $1,353.00