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 $221.97   5.388%   $233.9297   $233.93   $233.95   $233.90  
  Purchase #2 $73.43   3.874%   $76.2747   $76.27   $76.25   $76.30  
  Purchase #3 $35.82   5.372%   $37.7443   $37.74   $37.75   $37.70  
  Purchase #4 $80.33   9.511%   $87.9702   $87.97   $87.95   $88.00  
  Purchase #5 $29.64   13.719%   $33.7063   $33.71   $33.70   $33.70  
  Purchase #6 $169.64   9.654%   $186.017   $186.02   $186.00   $186.00  
  Purchase #7 $116.73   3.464%   $120.7735   $120.77   $120.75   $120.80  
  7 purchase totals = $727.56       $776.4157   $776.41   $776.35   $776.40