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 $82.27   12.870%   $92.8581   $92.86   $92.85   $92.90  
  Purchase #2 $213.97   10.119%   $235.6216   $235.62   $235.60   $235.60  
  Purchase #3 $109.46   8.419%   $118.6754   $118.68   $118.70   $118.70  
  Purchase #4 $36.65   4.148%   $38.1702   $38.17   $38.15   $38.20  
  Purchase #5 $74.64   6.731%   $79.664   $79.66   $79.65   $79.70  
  Purchase #6 $245.48   6.242%   $260.8029   $260.80   $260.80   $260.80  
  Purchase #7 $247.82   9.851%   $272.2327   $272.23   $272.25   $272.20  
  7 purchase totals = $1,010.29       $1,098.0249   $1,098.02   $1,098.00   $1,098.10