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 $68.32   6.493%   $72.756   $72.76   $72.75   $72.80  
  Purchase #2 $148.67   5.529%   $156.89   $156.89   $156.90   $156.90  
  Purchase #3 $119.91   4.354%   $125.1309   $125.13   $125.15   $125.10  
  Purchase #4 $40.93   7.554%   $44.0219   $44.02   $44.00   $44.00  
  Purchase #5 $246.71   7.834%   $266.0373   $266.04   $266.05   $266.00  
  Purchase #6 $115.72   11.761%   $129.3298   $129.33   $129.35   $129.30  
  Purchase #7 $222.64   8.732%   $242.0809   $242.08   $242.10   $242.10  
  7 purchase totals = $962.90       $1,036.2468   $1,036.25   $1,036.30   $1,036.20