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 $85.69   12.634%   $96.5161   $96.52   $96.50   $96.50  
  Purchase #2 $157.98   6.407%   $168.1018   $168.10   $168.10   $168.10  
  Purchase #3 $202.91   4.176%   $211.3835   $211.38   $211.40   $211.40  
  Purchase #4 $201.27   5.443%   $212.2251   $212.23   $212.25   $212.20  
  Purchase #5 $122.69   9.205%   $133.9836   $133.98   $134.00   $134.00  
  Purchase #6 $94.44   4.317%   $98.517   $98.52   $98.50   $98.50  
  Purchase #7 $116.94   12.609%   $131.685   $131.69   $131.70   $131.70  
  7 purchase totals = $981.92       $1,052.4121   $1,052.42   $1,052.45   $1,052.40