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 $76.87   11.792%   $85.9345   $85.93   $85.95   $85.90  
  Purchase #2 $128.44   10.550%   $141.9904   $141.99   $142.00   $142.00  
  Purchase #3 $163.49   10.690%   $180.9671   $180.97   $180.95   $181.00  
  Purchase #4 $214.36   11.234%   $238.4412   $238.44   $238.45   $238.40  
  Purchase #5 $159.63   10.304%   $176.0783   $176.08   $176.10   $176.10  
  Purchase #6 $201.98   4.511%   $211.0913   $211.09   $211.10   $211.10  
  Purchase #7 $63.28   5.343%   $66.6611   $66.66   $66.65   $66.70  
  7 purchase totals = $1,008.05       $1,101.1639   $1,101.16   $1,101.20   $1,101.20