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 $77.35   11.249%   $86.0511   $86.05   $86.05   $86.10  
  Purchase #2 $216.90   9.809%   $238.1757   $238.18   $238.20   $238.20  
  Purchase #3 $223.28   9.569%   $244.6457   $244.65   $244.65   $244.60  
  Purchase #4 $132.51   3.832%   $137.5878   $137.59   $137.60   $137.60  
  Purchase #5 $43.44   8.779%   $47.2536   $47.25   $47.25   $47.30  
  Purchase #6 $165.41   4.619%   $173.0503   $173.05   $173.05   $173.10  
  Purchase #7 $94.49   13.436%   $107.1857   $107.19   $107.20   $107.20  
  7 purchase totals = $953.38       $1,033.9499   $1,033.96   $1,034.00   $1,034.10