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 $93.77   5.216%   $98.661   $98.66   $98.65   $98.70  
  Purchase #2 $71.46   5.147%   $75.138   $75.14   $75.15   $75.10  
  Purchase #3 $192.43   5.476%   $202.9675   $202.97   $202.95   $203.00  
  Purchase #4 $118.58   13.265%   $134.3096   $134.31   $134.30   $134.30  
  Purchase #5 $53.42   7.784%   $57.5782   $57.58   $57.60   $57.60  
  Purchase #6 $239.75   5.239%   $252.3105   $252.31   $252.30   $252.30  
  Purchase #7 $12.92   8.633%   $14.0354   $14.04   $14.05   $14.00  
  7 purchase totals = $782.33       $835.0002   $835.01   $835.00   $835.00