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 $211.41   10.272%   $233.126   $233.13   $233.15   $233.10  
  Purchase #2 $44.58   10.339%   $49.1891   $49.19   $49.20   $49.20  
  Purchase #3 $67.72   8.709%   $73.6177   $73.62   $73.60   $73.60  
  Purchase #4 $182.90   9.347%   $199.9957   $200.00   $200.00   $200.00  
  Purchase #5 $54.26   5.695%   $57.3501   $57.35   $57.35   $57.40  
  Purchase #6 $244.51   4.861%   $256.3956   $256.40   $256.40   $256.40  
  Purchase #7 $155.54   10.350%   $171.6384   $171.64   $171.65   $171.60  
  7 purchase totals = $960.92       $1,041.3126   $1,041.33   $1,041.35   $1,041.30