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 $85.74   9.690%   $94.0482   $94.05   $94.05   $94.00  
  Purchase #2 $162.83   11.707%   $181.8925   $181.89   $181.90   $181.90  
  Purchase #3 $167.68   4.506%   $175.2357   $175.24   $175.25   $175.20  
  Purchase #4 $213.71   10.277%   $235.673   $235.67   $235.65   $235.70  
  Purchase #5 $223.88   11.600%   $249.8501   $249.85   $249.85   $249.90  
  Purchase #6 $140.70   5.268%   $148.1121   $148.11   $148.10   $148.10  
  Purchase #7 $10.33   11.712%   $11.5398   $11.54   $11.55   $11.50  
  7 purchase totals = $1,004.87       $1,096.3514   $1,096.35   $1,096.35   $1,096.30