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 $208.66   9.573%   $228.635   $228.64   $228.65   $228.60  
  Purchase #2 $72.54   7.273%   $77.8158   $77.82   $77.80   $77.80  
  Purchase #3 $180.56   7.764%   $194.5787   $194.58   $194.60   $194.60  
  Purchase #4 $175.89   9.294%   $192.2372   $192.24   $192.25   $192.20  
  Purchase #5 $174.79   11.540%   $194.9608   $194.96   $194.95   $195.00  
  Purchase #6 $6.34   13.680%   $7.2073   $7.21   $7.20   $7.20  
  Purchase #7 $163.25   5.433%   $172.1194   $172.12   $172.10   $172.10  
  7 purchase totals = $982.03       $1,067.5542   $1,067.57   $1,067.55   $1,067.50