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 $82.26   4.142%   $85.6672   $85.67   $85.65   $85.70  
  Purchase #2 $179.68   9.606%   $196.9401   $196.94   $196.95   $196.90  
  Purchase #3 $87.53   6.319%   $93.061   $93.06   $93.05   $93.10  
  Purchase #4 $235.34   4.344%   $245.5632   $245.56   $245.55   $245.60  
  Purchase #5 $195.50   8.216%   $211.5623   $211.56   $211.55   $211.60  
  Purchase #6 $88.75   7.790%   $95.6636   $95.66   $95.65   $95.70  
  Purchase #7 $123.85   10.272%   $136.5719   $136.57   $136.55   $136.60  
  7 purchase totals = $992.91       $1,065.0293   $1,065.02   $1,064.95   $1,065.20