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 $47.83   11.359%   $53.263   $53.26   $53.25   $53.30  
  Purchase #2 $187.91   7.777%   $202.5238   $202.52   $202.50   $202.50  
  Purchase #3 $17.94   7.463%   $19.2789   $19.28   $19.30   $19.30  
  Purchase #4 $169.99   5.831%   $179.9021   $179.90   $179.90   $179.90  
  Purchase #5 $159.62   11.372%   $177.772   $177.77   $177.75   $177.80  
  Purchase #6 $199.44   7.430%   $214.2584   $214.26   $214.25   $214.30  
  Purchase #7 $176.82   4.810%   $185.325   $185.33   $185.35   $185.30  
  7 purchase totals = $959.55       $1,032.3232   $1,032.32   $1,032.30   $1,032.40