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 $46.45   3.518%   $48.0841   $48.08   $48.10   $48.10  
  Purchase #2 $114.33   7.580%   $122.9962   $123.00   $123.00   $123.00  
  Purchase #3 $180.64   3.537%   $187.0292   $187.03   $187.05   $187.00  
  Purchase #4 $247.59   3.461%   $256.1591   $256.16   $256.15   $256.20  
  Purchase #5 $82.48   13.229%   $93.3913   $93.39   $93.40   $93.40  
  Purchase #6 $232.82   11.348%   $259.2404   $259.24   $259.25   $259.20  
  Purchase #7 $60.98   8.613%   $66.2322   $66.23   $66.25   $66.20  
  7 purchase totals = $965.29       $1,033.1325   $1,033.13   $1,033.20   $1,033.10