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 $63.89   5.801%   $67.5963   $67.60   $67.60   $67.60  
  Purchase #2 $170.64   3.239%   $176.167   $176.17   $176.15   $176.20  
  Purchase #3 $45.26   10.872%   $50.1807   $50.18   $50.20   $50.20  
  Purchase #4 $210.82   6.361%   $224.2303   $224.23   $224.25   $224.20  
  Purchase #5 $34.77   8.282%   $37.6497   $37.65   $37.65   $37.60  
  Purchase #6 $248.38   3.625%   $257.3838   $257.38   $257.40   $257.40  
  Purchase #7 $194.67   5.833%   $206.0251   $206.03   $206.05   $206.00  
  7 purchase totals = $968.43       $1,019.2329   $1,019.24   $1,019.30   $1,019.20