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 $85.67   10.809%   $94.9301   $94.93   $94.95   $94.90  
  Purchase #2 $161.28   13.276%   $182.6915   $182.69   $182.70   $182.70  
  Purchase #3 $74.55   3.318%   $77.0236   $77.02   $77.00   $77.00  
  Purchase #4 $220.73   11.315%   $245.7056   $245.71   $245.70   $245.70  
  Purchase #5 $124.85   11.526%   $139.2402   $139.24   $139.25   $139.20  
  Purchase #6 $179.88   12.690%   $202.7068   $202.71   $202.70   $202.70  
  Purchase #7 $112.90   4.825%   $118.3474   $118.35   $118.35   $118.30  
  7 purchase totals = $959.86       $1,060.6452   $1,060.65   $1,060.65   $1,060.50