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 $66.25   11.623%   $73.9502   $73.95   $73.95   $74.00  
  Purchase #2 $155.65   12.444%   $175.0191   $175.02   $175.00   $175.00  
  Purchase #3 $90.50   4.351%   $94.4377   $94.44   $94.45   $94.40  
  Purchase #4 $248.90   10.504%   $275.0445   $275.04   $275.05   $275.00  
  Purchase #5 $44.98   7.141%   $48.192   $48.19   $48.20   $48.20  
  Purchase #6 $153.42   6.348%   $163.1591   $163.16   $163.15   $163.20  
  Purchase #7 $190.97   13.229%   $216.2334   $216.23   $216.25   $216.20  
  7 purchase totals = $950.67       $1,046.0360   $1,046.03   $1,046.05   $1,046.00