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 $95.89   9.464%   $104.965   $104.97   $104.95   $105.00  
  Purchase #2 $9.75   9.134%   $10.6406   $10.64   $10.65   $10.60  
  Purchase #3 $25.30   6.672%   $26.988   $26.99   $27.00   $27.00  
  Purchase #4 $86.71   6.736%   $92.5508   $92.55   $92.55   $92.60  
  Purchase #5 $248.58   11.734%   $277.7484   $277.75   $277.75   $277.70  
  Purchase #6 $98.85   5.399%   $104.1869   $104.19   $104.20   $104.20  
  Purchase #7 $121.87   7.130%   $130.5593   $130.56   $130.55   $130.60  
  7 purchase totals = $686.95       $747.6390   $747.65   $747.65   $747.70