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 $183.96   9.592%   $201.6054   $201.61   $201.60   $201.60  
  Purchase #2 $157.97   9.264%   $172.6043   $172.60   $172.60   $172.60  
  Purchase #3 $81.59   3.806%   $84.6953   $84.70   $84.70   $84.70  
  Purchase #4 $22.47   11.511%   $25.0565   $25.06   $25.05   $25.10  
  Purchase #5 $105.85   9.761%   $116.182   $116.18   $116.20   $116.20  
  Purchase #6 $117.72   5.582%   $124.2911   $124.29   $124.30   $124.30  
  Purchase #7 $46.30   7.796%   $49.9095   $49.91   $49.90   $49.90  
  7 purchase totals = $715.86       $774.3441   $774.35   $774.35   $774.40