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 $186.70   3.244%   $192.7565   $192.76   $192.75   $192.80  
  Purchase #2 $207.92   3.243%   $214.6628   $214.66   $214.65   $214.70  
  Purchase #3 $211.53   8.368%   $229.2308   $229.23   $229.25   $229.20  
  Purchase #4 $232.37   11.168%   $258.3211   $258.32   $258.30   $258.30  
  Purchase #5 $45.89   9.189%   $50.1068   $50.11   $50.10   $50.10  
  Purchase #6 $69.98   3.346%   $72.3215   $72.32   $72.30   $72.30  
  Purchase #7 $195.52   3.367%   $202.1032   $202.10   $202.10   $202.10  
  7 purchase totals = $1,149.91       $1,219.5027   $1,219.50   $1,219.45   $1,219.50