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 $163.55   8.263%   $177.0641   $177.06   $177.05   $177.10  
  Purchase #2 $96.43   10.781%   $106.8261   $106.83   $106.85   $106.80  
  Purchase #3 $24.40   8.172%   $26.394   $26.39   $26.40   $26.40  
  Purchase #4 $234.82   7.144%   $251.5955   $251.60   $251.60   $251.60  
  Purchase #5 $112.83   7.258%   $121.0192   $121.02   $121.00   $121.00  
  Purchase #6 $183.59   4.727%   $192.2683   $192.27   $192.25   $192.30  
  Purchase #7 $216.87   8.761%   $235.87   $235.87   $235.85   $235.90  
  7 purchase totals = $1,032.49       $1,111.0372   $1,111.04   $1,111.00   $1,111.10