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 $117.95   6.535%   $125.658   $125.66   $125.65   $125.70  
  Purchase #2 $216.72   5.683%   $229.0362   $229.04   $229.05   $229.00  
  Purchase #3 $24.30   5.651%   $25.6732   $25.67   $25.65   $25.70  
  Purchase #4 $177.62   8.416%   $192.5685   $192.57   $192.55   $192.60  
  Purchase #5 $144.55   11.370%   $160.9853   $160.99   $161.00   $161.00  
  Purchase #6 $74.98   3.772%   $77.8082   $77.81   $77.80   $77.80  
  Purchase #7 $213.94   3.507%   $221.4429   $221.44   $221.45   $221.40  
  7 purchase totals = $970.06       $1,033.1723   $1,033.18   $1,033.15   $1,033.20