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 $55.62   11.392%   $61.9562   $61.96   $61.95   $62.00  
  Purchase #2 $134.86   12.213%   $151.3305   $151.33   $151.35   $151.30  
  Purchase #3 $82.60   11.181%   $91.8355   $91.84   $91.85   $91.80  
  Purchase #4 $114.57   6.432%   $121.9391   $121.94   $121.95   $121.90  
  Purchase #5 $154.88   5.831%   $163.9111   $163.91   $163.90   $163.90  
  Purchase #6 $190.32   3.554%   $197.084   $197.08   $197.10   $197.10  
  Purchase #7 $234.37   9.324%   $256.2227   $256.22   $256.20   $256.20  
  7 purchase totals = $967.22       $1,044.2791   $1,044.28   $1,044.30   $1,044.20