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 $96.31   5.797%   $101.8931   $101.89   $101.90   $101.90  
  Purchase #2 $229.87   5.670%   $242.9036   $242.90   $242.90   $242.90  
  Purchase #3 $159.49   11.378%   $177.6368   $177.64   $177.65   $177.60  
  Purchase #4 $43.37   7.564%   $46.6505   $46.65   $46.65   $46.70  
  Purchase #5 $86.37   7.635%   $92.9643   $92.96   $92.95   $93.00  
  Purchase #6 $106.59   6.667%   $113.6964   $113.70   $113.70   $113.70  
  Purchase #7 $221.36   12.753%   $249.59   $249.59   $249.60   $249.60  
  7 purchase totals = $943.36       $1,025.3347   $1,025.33   $1,025.35   $1,025.40