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 $83.87   12.647%   $94.477   $94.48   $94.50   $94.50  
  Purchase #2 $54.26   4.628%   $56.7712   $56.77   $56.75   $56.80  
  Purchase #3 $165.76   8.145%   $179.2612   $179.26   $179.25   $179.30  
  Purchase #4 $171.59   12.344%   $192.7711   $192.77   $192.75   $192.80  
  Purchase #5 $79.31   3.523%   $82.1041   $82.10   $82.10   $82.10  
  Purchase #6 $166.93   10.480%   $184.4243   $184.42   $184.40   $184.40  
  Purchase #7 $156.91   4.137%   $163.4014   $163.40   $163.40   $163.40  
  7 purchase totals = $878.63       $953.2103   $953.20   $953.15   $953.30