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 $238.99   3.184%   $246.5994   $246.60   $246.60   $246.60  
  Purchase #2 $150.58   9.816%   $165.3609   $165.36   $165.35   $165.40  
  Purchase #3 $100.96   13.571%   $114.6613   $114.66   $114.65   $114.70  
  Purchase #4 $59.92   10.508%   $66.2164   $66.22   $66.20   $66.20  
  Purchase #5 $77.59   4.643%   $81.1925   $81.19   $81.20   $81.20  
  Purchase #6 $212.38   3.701%   $220.2402   $220.24   $220.25   $220.20  
  Purchase #7 $189.57   6.372%   $201.6494   $201.65   $201.65   $201.60  
  7 purchase totals = $1,029.99       $1,095.9201   $1,095.92   $1,095.90   $1,095.90