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 $64.36   5.278%   $67.7569   $67.76   $67.75   $67.80  
  Purchase #2 $166.79   7.632%   $179.5194   $179.52   $179.50   $179.50  
  Purchase #3 $207.87   12.226%   $233.2842   $233.28   $233.30   $233.30  
  Purchase #4 $85.74   8.107%   $92.6909   $92.69   $92.70   $92.70  
  Purchase #5 $62.33   6.191%   $66.1889   $66.19   $66.20   $66.20  
  Purchase #6 $225.55   4.755%   $236.2749   $236.27   $236.25   $236.30  
  Purchase #7 $156.88   13.102%   $177.4344   $177.43   $177.45   $177.40  
  7 purchase totals = $969.52       $1,053.1496   $1,053.14   $1,053.15   $1,053.20