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 $88.80   7.667%   $95.6083   $95.61   $95.60   $95.60  
  Purchase #2 $77.85   9.784%   $85.4668   $85.47   $85.45   $85.50  
  Purchase #3 $151.52   9.304%   $165.6174   $165.62   $165.60   $165.60  
  Purchase #4 $245.32   13.603%   $278.6909   $278.69   $278.70   $278.70  
  Purchase #5 $164.35   7.106%   $176.0287   $176.03   $176.05   $176.00  
  Purchase #6 $244.55   13.458%   $277.4615   $277.46   $277.45   $277.50  
  Purchase #7 $217.67   10.481%   $240.484   $240.48   $240.50   $240.50  
  7 purchase totals = $1,190.06       $1,319.3576   $1,319.36   $1,319.35   $1,319.40