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 $86.98   11.235%   $96.7522   $96.75   $96.75   $96.80  
  Purchase #2 $191.62   10.348%   $211.4488   $211.45   $211.45   $211.40  
  Purchase #3 $60.40   6.328%   $64.2221   $64.22   $64.20   $64.20  
  Purchase #4 $69.49   11.467%   $77.4584   $77.46   $77.45   $77.50  
  Purchase #5 $125.86   3.253%   $129.9542   $129.95   $129.95   $130.00  
  Purchase #6 $9.41   10.796%   $10.4259   $10.43   $10.45   $10.40  
  Purchase #7 $243.62   12.215%   $273.3782   $273.38   $273.40   $273.40  
  7 purchase totals = $787.38       $863.6398   $863.64   $863.65   $863.70