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 $211.69   7.318%   $227.1815   $227.18   $227.20   $227.20  
  Purchase #2 $196.99   6.576%   $209.9441   $209.94   $209.95   $209.90  
  Purchase #3 $149.80   7.580%   $161.1548   $161.15   $161.15   $161.20  
  Purchase #4 $145.58   13.467%   $165.1853   $165.19   $165.20   $165.20  
  Purchase #5 $236.75   7.633%   $254.8211   $254.82   $254.80   $254.80  
  Purchase #6 $106.65   9.698%   $116.9929   $116.99   $117.00   $117.00  
  Purchase #7 $63.70   3.785%   $66.111   $66.11   $66.10   $66.10  
  7 purchase totals = $1,111.16       $1,201.3907   $1,201.38   $1,201.40   $1,201.40