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 $199.38   5.289%   $209.9252   $209.93   $209.95   $209.90  
  Purchase #2 $55.65   11.618%   $62.1154   $62.12   $62.10   $62.10  
  Purchase #3 $46.32   7.757%   $49.913   $49.91   $49.90   $49.90  
  Purchase #4 $142.27   7.384%   $152.7752   $152.78   $152.80   $152.80  
  Purchase #5 $167.47   8.827%   $182.2526   $182.25   $182.25   $182.30  
  Purchase #6 $204.96   8.337%   $222.0475   $222.05   $222.05   $222.00  
  Purchase #7 $195.97   4.108%   $204.0204   $204.02   $204.00   $204.00  
  7 purchase totals = $1,012.02       $1,083.0493   $1,083.06   $1,083.05   $1,083.00