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 $184.88   6.156%   $196.2612   $196.26   $196.25   $196.30  
  Purchase #2 $236.85   4.149%   $246.6769   $246.68   $246.70   $246.70  
  Purchase #3 $15.50   6.438%   $16.4979   $16.50   $16.50   $16.50  
  Purchase #4 $147.73   9.820%   $162.2371   $162.24   $162.25   $162.20  
  Purchase #5 $73.79   12.443%   $82.9717   $82.97   $82.95   $83.00  
  Purchase #6 $211.61   4.688%   $221.5303   $221.53   $221.55   $221.50  
  Purchase #7 $207.33   6.171%   $220.1243   $220.12   $220.10   $220.10  
  7 purchase totals = $1,077.69       $1,146.2994   $1,146.30   $1,146.30   $1,146.30