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 $214.52   12.485%   $241.3028   $241.30   $241.30   $241.30  
  Purchase #2 $169.26   4.454%   $176.7988   $176.80   $176.80   $176.80  
  Purchase #3 $17.54   12.844%   $19.7928   $19.79   $19.80   $19.80  
  Purchase #4 $191.28   8.793%   $208.0993   $208.10   $208.10   $208.10  
  Purchase #5 $45.72   8.791%   $49.7392   $49.74   $49.75   $49.70  
  Purchase #6 $99.68   5.557%   $105.2192   $105.22   $105.20   $105.20  
  Purchase #7 $160.25   7.120%   $171.6598   $171.66   $171.65   $171.70  
  7 purchase totals = $898.25       $972.6119   $972.61   $972.60   $972.60