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 $97.86   5.858%   $103.5926   $103.59   $103.60   $103.60  
  Purchase #2 $213.31   10.562%   $235.8398   $235.84   $235.85   $235.80  
  Purchase #3 $23.45   12.731%   $26.4354   $26.44   $26.45   $26.40  
  Purchase #4 $197.53   3.337%   $204.1216   $204.12   $204.10   $204.10  
  Purchase #5 $175.63   6.401%   $186.8721   $186.87   $186.85   $186.90  
  Purchase #6 $239.98   9.433%   $262.6173   $262.62   $262.60   $262.60  
  Purchase #7 $128.48   13.504%   $145.8299   $145.83   $145.85   $145.80  
  7 purchase totals = $1,076.24       $1,165.3087   $1,165.31   $1,165.30   $1,165.20