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 $88.68   6.335%   $94.2979   $94.30   $94.30   $94.30  
  Purchase #2 $190.70   5.441%   $201.076   $201.08   $201.10   $201.10  
  Purchase #3 $113.52   4.296%   $118.3968   $118.40   $118.40   $118.40  
  Purchase #4 $212.87   6.655%   $227.0365   $227.04   $227.05   $227.00  
  Purchase #5 $183.81   13.689%   $208.9718   $208.97   $208.95   $209.00  
  Purchase #6 $221.54   6.526%   $235.9977   $236.00   $236.00   $236.00  
  Purchase #7 $170.25   7.540%   $183.0869   $183.09   $183.10   $183.10  
  7 purchase totals = $1,181.37       $1,268.8636   $1,268.88   $1,268.90   $1,268.90