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 $56.29   10.475%   $62.1864   $62.19   $62.20   $62.20  
  Purchase #2 $214.38   7.776%   $231.0502   $231.05   $231.05   $231.10  
  Purchase #3 $159.47   9.344%   $174.3709   $174.37   $174.35   $174.40  
  Purchase #4 $141.96   12.419%   $159.59   $159.59   $159.60   $159.60  
  Purchase #5 $117.98   9.377%   $129.043   $129.04   $129.05   $129.00  
  Purchase #6 $164.64   3.328%   $170.1192   $170.12   $170.10   $170.10  
  Purchase #7 $200.34   13.744%   $227.8747   $227.87   $227.85   $227.90  
  7 purchase totals = $1,055.06       $1,154.2344   $1,154.23   $1,154.20   $1,154.30