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 $105.38   13.504%   $119.6105   $119.61   $119.60   $119.60  
  Purchase #2 $109.33   6.564%   $116.5064   $116.51   $116.50   $116.50  
  Purchase #3 $194.45   10.415%   $214.702   $214.70   $214.70   $214.70  
  Purchase #4 $239.72   10.176%   $264.1139   $264.11   $264.10   $264.10  
  Purchase #5 $68.78   3.102%   $70.9136   $70.91   $70.90   $70.90  
  Purchase #6 $204.98   9.245%   $223.9304   $223.93   $223.95   $223.90  
  Purchase #7 $61.62   3.526%   $63.7927   $63.79   $63.80   $63.80  
  7 purchase totals = $984.26       $1,073.5695   $1,073.56   $1,073.55   $1,073.50