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 $196.80   5.153%   $206.9411   $206.94   $206.95   $206.90  
  Purchase #2 $233.79   7.622%   $251.6095   $251.61   $251.60   $251.60  
  Purchase #3 $149.51   8.784%   $162.643   $162.64   $162.65   $162.60  
  Purchase #4 $218.52   7.748%   $235.4509   $235.45   $235.45   $235.50  
  Purchase #5 $94.47   10.631%   $104.5131   $104.51   $104.50   $104.50  
  Purchase #6 $62.32   5.684%   $65.8623   $65.86   $65.85   $65.90  
  Purchase #7 $101.34   5.812%   $107.2299   $107.23   $107.25   $107.20  
  7 purchase totals = $1,056.75       $1,134.2498   $1,134.24   $1,134.25   $1,134.20