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 $174.61   11.736%   $195.1022   $195.10   $195.10   $195.10  
  Purchase #2 $129.88   11.392%   $144.6759   $144.68   $144.70   $144.70  
  Purchase #3 $146.74   4.632%   $153.537   $153.54   $153.55   $153.50  
  Purchase #4 $53.44   4.431%   $55.8079   $55.81   $55.80   $55.80  
  Purchase #5 $192.67   6.616%   $205.417   $205.42   $205.40   $205.40  
  Purchase #6 $228.97   6.663%   $244.2263   $244.23   $244.25   $244.20  
  Purchase #7 $162.68   13.829%   $185.177   $185.18   $185.20   $185.20  
  7 purchase totals = $1,088.99       $1,183.9433   $1,183.96   $1,184.00   $1,183.90