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 $86.91   9.273%   $94.9692   $94.97   $94.95   $95.00  
  Purchase #2 $121.83   5.366%   $128.3674   $128.37   $128.35   $128.40  
  Purchase #3 $190.84   13.196%   $216.0232   $216.02   $216.00   $216.00  
  Purchase #4 $186.28   4.710%   $195.0538   $195.05   $195.05   $195.10  
  Purchase #5 $161.94   6.581%   $172.5973   $172.60   $172.60   $172.60  
  Purchase #6 $73.60   10.672%   $81.4546   $81.45   $81.45   $81.50  
  Purchase #7 $127.47   4.642%   $133.3872   $133.39   $133.40   $133.40  
  7 purchase totals = $948.87       $1,021.8527   $1,021.85   $1,021.80   $1,022.00