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 $61.39   13.560%   $69.7145   $69.71   $69.70   $69.70  
  Purchase #2 $101.95   4.356%   $106.3909   $106.39   $106.40   $106.40  
  Purchase #3 $193.51   8.822%   $210.5815   $210.58   $210.60   $210.60  
  Purchase #4 $196.69   12.825%   $221.9155   $221.92   $221.90   $221.90  
  Purchase #5 $168.64   3.800%   $175.0483   $175.05   $175.05   $175.00  
  Purchase #6 $18.42   12.735%   $20.7658   $20.77   $20.75   $20.80  
  Purchase #7 $197.74   9.349%   $216.2267   $216.23   $216.25   $216.20  
  7 purchase totals = $938.34       $1,020.6432   $1,020.65   $1,020.65   $1,020.60