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 $76.75   11.619%   $85.6676   $85.67   $85.65   $85.70  
  Purchase #2 $38.99   12.361%   $43.8096   $43.81   $43.80   $43.80  
  Purchase #3 $218.55   3.435%   $226.0572   $226.06   $226.05   $226.10  
  Purchase #4 $173.43   6.643%   $184.951   $184.95   $184.95   $185.00  
  Purchase #5 $39.82   3.266%   $41.1205   $41.12   $41.10   $41.10  
  Purchase #6 $129.84   10.677%   $143.703   $143.70   $143.70   $143.70  
  Purchase #7 $196.88   9.519%   $215.621   $215.62   $215.60   $215.60  
  7 purchase totals = $874.26       $940.9299   $940.93   $940.85   $941.00