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 $87.53   5.335%   $92.1997   $92.20   $92.20   $92.20  
  Purchase #2 $82.94   11.127%   $92.1687   $92.17   $92.15   $92.20  
  Purchase #3 $216.88   9.521%   $237.5291   $237.53   $237.55   $237.50  
  Purchase #4 $237.94   8.466%   $258.084   $258.08   $258.10   $258.10  
  Purchase #5 $131.76   5.508%   $139.0173   $139.02   $139.00   $139.00  
  Purchase #6 $97.49   5.618%   $102.967   $102.97   $102.95   $103.00  
  Purchase #7 $82.40   7.472%   $88.5569   $88.56   $88.55   $88.60  
  7 purchase totals = $936.94       $1,010.5227   $1,010.53   $1,010.50   $1,010.60