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 $127.69   5.413%   $134.6019   $134.60   $134.60   $134.60  
  Purchase #2 $221.74   3.136%   $228.6938   $228.69   $228.70   $228.70  
  Purchase #3 $100.42   9.510%   $109.9699   $109.97   $109.95   $110.00  
  Purchase #4 $21.57   7.527%   $23.1936   $23.19   $23.20   $23.20  
  Purchase #5 $134.38   5.680%   $142.0128   $142.01   $142.00   $142.00  
  Purchase #6 $163.53   4.304%   $170.5683   $170.57   $170.55   $170.60  
  Purchase #7 $240.75   5.361%   $253.6566   $253.66   $253.65   $253.70  
  7 purchase totals = $1,010.08       $1,062.6969   $1,062.69   $1,062.65   $1,062.80