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 $58.31   5.523%   $61.5305   $61.53   $61.55   $61.50  
  Purchase #2 $198.52   10.289%   $218.9457   $218.95   $218.95   $218.90  
  Purchase #3 $249.37   5.713%   $263.6165   $263.62   $263.60   $263.60  
  Purchase #4 $187.94   12.559%   $211.5434   $211.54   $211.55   $211.50  
  Purchase #5 $22.94   13.527%   $26.0431   $26.04   $26.05   $26.00  
  Purchase #6 $212.80   12.868%   $240.1831   $240.18   $240.20   $240.20  
  Purchase #7 $154.80   5.718%   $163.6515   $163.65   $163.65   $163.70  
  7 purchase totals = $1,084.68       $1,185.5138   $1,185.51   $1,185.55   $1,185.40