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 $95.69   8.262%   $103.5959   $103.60   $103.60   $103.60  
  Purchase #2 $48.93   9.483%   $53.57   $53.57   $53.55   $53.60  
  Purchase #3 $64.82   5.698%   $68.5134   $68.51   $68.50   $68.50  
  Purchase #4 $111.38   4.589%   $116.4912   $116.49   $116.50   $116.50  
  Purchase #5 $193.26   10.767%   $214.0683   $214.07   $214.05   $214.10  
  Purchase #6 $152.62   10.151%   $168.1125   $168.11   $168.10   $168.10  
  Purchase #7 $11.58   10.132%   $12.7533   $12.75   $12.75   $12.80  
  7 purchase totals = $678.28       $737.1046   $737.10   $737.05   $737.20