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 $59.76   13.853%   $68.0386   $68.04   $68.05   $68.00  
  Purchase #2 $119.73   5.247%   $126.0122   $126.01   $126.00   $126.00  
  Purchase #3 $217.95   6.599%   $232.3325   $232.33   $232.35   $232.30  
  Purchase #4 $232.37   8.282%   $251.6149   $251.61   $251.60   $251.60  
  Purchase #5 $38.80   3.527%   $40.1685   $40.17   $40.15   $40.20  
  Purchase #6 $182.52   11.725%   $203.9205   $203.92   $203.90   $203.90  
  Purchase #7 $173.43   6.542%   $184.7758   $184.78   $184.80   $184.80  
  7 purchase totals = $1,024.56       $1,106.8630   $1,106.86   $1,106.85   $1,106.80