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 $153.38   13.837%   $174.6032   $174.60   $174.60   $174.60  
  Purchase #2 $133.46   9.324%   $145.9038   $145.90   $145.90   $145.90  
  Purchase #3 $219.58   3.210%   $226.6285   $226.63   $226.65   $226.60  
  Purchase #4 $169.67   9.351%   $185.5358   $185.54   $185.55   $185.50  
  Purchase #5 $190.81   3.415%   $197.3262   $197.33   $197.35   $197.30  
  Purchase #6 $191.55   7.197%   $205.3359   $205.34   $205.35   $205.30  
  Purchase #7 $39.54   4.365%   $41.2659   $41.27   $41.25   $41.30  
  7 purchase totals = $1,097.99       $1,176.5993   $1,176.61   $1,176.65   $1,176.50