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 $60.88   3.298%   $62.8878   $62.89   $62.90   $62.90  
  Purchase #2 $210.65   11.395%   $234.6536   $234.65   $234.65   $234.70  
  Purchase #3 $111.39   3.118%   $114.8631   $114.86   $114.85   $114.90  
  Purchase #4 $69.94   7.273%   $75.0267   $75.03   $75.05   $75.00  
  Purchase #5 $238.42   6.263%   $253.3522   $253.35   $253.35   $253.40  
  Purchase #6 $77.88   7.463%   $83.6922   $83.69   $83.70   $83.70  
  Purchase #7 $120.83   7.573%   $129.9805   $129.98   $130.00   $130.00  
  7 purchase totals = $889.99       $954.4561   $954.45   $954.50   $954.60