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 $79.49   8.124%   $85.9478   $85.95   $85.95   $85.90  
  Purchase #2 $170.99   9.348%   $186.9741   $186.97   $186.95   $187.00  
  Purchase #3 $227.87   3.822%   $236.5792   $236.58   $236.60   $236.60  
  Purchase #4 $183.52   8.805%   $199.6789   $199.68   $199.70   $199.70  
  Purchase #5 $145.56   6.780%   $155.429   $155.43   $155.45   $155.40  
  Purchase #6 $182.41   6.850%   $194.9051   $194.91   $194.90   $194.90  
  Purchase #7 $138.46   12.284%   $155.4684   $155.47   $155.45   $155.50  
  7 purchase totals = $1,128.30       $1,214.9825   $1,214.99   $1,215.00   $1,215.00