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 $192.34   4.832%   $201.6339   $201.63   $201.65   $201.60  
  Purchase #2 $221.95   10.232%   $244.6599   $244.66   $244.65   $244.70  
  Purchase #3 $143.76   13.751%   $163.5284   $163.53   $163.55   $163.50  
  Purchase #4 $136.97   12.251%   $153.7502   $153.75   $153.75   $153.80  
  Purchase #5 $80.99   5.257%   $85.2476   $85.25   $85.25   $85.20  
  Purchase #6 $65.43   5.745%   $69.189   $69.19   $69.20   $69.20  
  Purchase #7 $241.85   5.357%   $254.8059   $254.81   $254.80   $254.80  
  7 purchase totals = $1,083.29       $1,172.8149   $1,172.82   $1,172.85   $1,172.80