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 $63.84   10.794%   $70.7309   $70.73   $70.75   $70.70  
  Purchase #2 $194.79   11.292%   $216.7857   $216.79   $216.80   $216.80  
  Purchase #3 $62.79   6.318%   $66.7571   $66.76   $66.75   $66.80  
  Purchase #4 $173.99   6.191%   $184.7617   $184.76   $184.75   $184.80  
  Purchase #5 $248.98   6.638%   $265.5073   $265.51   $265.50   $265.50  
  Purchase #6 $238.74   11.326%   $265.7797   $265.78   $265.80   $265.80  
  Purchase #7 $5.94   10.691%   $6.575   $6.58   $6.60   $6.60  
  7 purchase totals = $989.07       $1,076.8974   $1,076.91   $1,076.95   $1,077.00