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 $112.52   6.320%   $119.6313   $119.63   $119.65   $119.60  
  Purchase #2 $150.97   8.184%   $163.3254   $163.33   $163.35   $163.30  
  Purchase #3 $166.62   5.819%   $176.3156   $176.32   $176.30   $176.30  
  Purchase #4 $212.32   5.753%   $224.5348   $224.53   $224.55   $224.50  
  Purchase #5 $186.54   9.202%   $203.7054   $203.71   $203.70   $203.70  
  Purchase #6 $62.64   3.478%   $64.8186   $64.82   $64.80   $64.80  
  Purchase #7 $240.69   4.749%   $252.1204   $252.12   $252.10   $252.10  
  7 purchase totals = $1,132.30       $1,204.4515   $1,204.46   $1,204.45   $1,204.30