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 $161.46   8.146%   $174.6125   $174.61   $174.60   $174.60  
  Purchase #2 $181.58   4.766%   $190.2341   $190.23   $190.25   $190.20  
  Purchase #3 $205.88   13.673%   $234.03   $234.03   $234.05   $234.00  
  Purchase #4 $156.39   8.364%   $169.4705   $169.47   $169.45   $169.50  
  Purchase #5 $216.95   7.659%   $233.5662   $233.57   $233.55   $233.60  
  Purchase #6 $151.78   5.428%   $160.0186   $160.02   $160.00   $160.00  
  Purchase #7 $225.59   11.814%   $252.2412   $252.24   $252.25   $252.20  
  7 purchase totals = $1,299.63       $1,414.1731   $1,414.17   $1,414.15   $1,414.10