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 $224.48   4.677%   $234.9789   $234.98   $235.00   $235.00  
  Purchase #2 $108.72   7.294%   $116.65   $116.65   $116.65   $116.70  
  Purchase #3 $239.89   12.190%   $269.1326   $269.13   $269.15   $269.10  
  Purchase #4 $229.50   11.742%   $256.4479   $256.45   $256.45   $256.40  
  Purchase #5 $52.87   5.357%   $55.7022   $55.70   $55.70   $55.70  
  Purchase #6 $48.71   13.328%   $55.2021   $55.20   $55.20   $55.20  
  Purchase #7 $154.39   7.426%   $165.855   $165.86   $165.85   $165.90  
  7 purchase totals = $1,058.56       $1,153.9687   $1,153.97   $1,154.00   $1,154.00