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 $83.77   13.379%   $94.9776   $94.98   $95.00   $95.00  
  Purchase #2 $125.48   3.373%   $129.7124   $129.71   $129.70   $129.70  
  Purchase #3 $70.35   4.450%   $73.4806   $73.48   $73.50   $73.50  
  Purchase #4 $245.49   5.120%   $258.0591   $258.06   $258.05   $258.10  
  Purchase #5 $120.30   3.825%   $124.9015   $124.90   $124.90   $124.90  
  Purchase #6 $85.60   7.408%   $91.9412   $91.94   $91.95   $91.90  
  Purchase #7 $207.88   11.170%   $231.1002   $231.10   $231.10   $231.10  
  7 purchase totals = $938.87       $1,004.1726   $1,004.17   $1,004.20   $1,004.20