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 $56.34   11.115%   $62.6022   $62.60   $62.60   $62.60  
  Purchase #2 $118.38   3.349%   $122.3445   $122.34   $122.35   $122.30  
  Purchase #3 $178.92   8.693%   $194.4735   $194.47   $194.45   $194.50  
  Purchase #4 $173.29   11.556%   $193.3154   $193.32   $193.30   $193.30  
  Purchase #5 $247.77   6.337%   $263.4712   $263.47   $263.45   $263.50  
  Purchase #6 $115.70   7.644%   $124.5441   $124.54   $124.55   $124.50  
  Purchase #7 $204.81   8.553%   $222.3274   $222.33   $222.35   $222.30  
  7 purchase totals = $1,095.21       $1,183.0783   $1,183.07   $1,183.05   $1,183.00